Pregnancy Due Date Calculator

Estimate an expected due date (EDD), trimester ranges, and a simple pregnancy timeline from LMP, conception date, or IVF transfer date. Educational only, not medical advice or a substitute for prenatal care.

Estimates an expected due date, trimester ranges, and week-by-week timing based on user-entered dates. Uses simple calendar math (like counting weeks/days from a starting date). Does NOT replace ultrasound dating or advice from an OB/GYN, midwife, or other clinician. Not a diagnostic tool; only an educational estimate.

Enter Your Information

Dating Method *

First Day of Last Menstrual Period *

Average Cycle Length (days) (Optional)

Default is 28 days if not specified.

Optional Context (For warnings only)

Parity

Multiple pregnancy suspected (twins, etc.)High-risk pregnancy (user-indicated)

Reference Date (Optional)

Default is today. Used to calculate current gestational age.

Choose a dating method and enter your dates to see an estimated due date and simple pregnancy timeline.

Understanding Pregnancy Due Dates: A Comprehensive Guide to EDD Calculation and Pregnancy Timeline

Last updated: December 16, 2025

An estimated due date (EDD) is the approximate date when a pregnancy is expected to reach full term (around 40 weeks from the start of the last menstrual period). It's a helpful reference point for tracking pregnancy progress, planning prenatal care, and preparing for the arrival of your baby. Understanding how due dates are calculated helps you make informed decisions about pregnancy planning and prenatal care. However, it's important to remember that due dates are estimates, not exact predictions—only about 5% of babies are born exactly on their due date.

Whether you're a student learning about pregnancy, a professional evaluating pregnancy timelines, a researcher studying obstetrics, a taxpayer understanding healthcare benefits, or a common person interested in pregnancy planning, understanding due date calculation provides valuable insights. Different methods (LMP, conception date, IVF transfer date, ultrasound) use different calculations to estimate due dates, which is why they produce different estimates. There is no single "correct" method—they are all estimates based on different assumptions. Understanding these methods helps you see pregnancy dating from multiple perspectives, not just a single date.

Our Pregnancy Due Date Calculator helps you estimate an expected due date (EDD), trimester ranges, and a simple pregnancy timeline from LMP, conception date, or IVF transfer date. Simply enter your last menstrual period (LMP), conception date, or IVF transfer date, and the calculator automatically computes your due date, current gestational age, trimester ranges, and key pregnancy milestones. You can also adjust for cycle length if your cycle differs from the standard 28 days. The calculator shows results with visual timelines and provides warnings about accuracy and limitations.

This tool is perfect for anyone who wants to understand due date calculation, track pregnancy progress, plan prenatal care, and make informed decisions about pregnancy. By calculating due dates from different starting points, you can see how different methods compare and understand pregnancy timelines. Remember, these are educational estimates based on simple calendar math—individual results may vary significantly. Always consult healthcare professionals for accurate due dates, especially those based on ultrasound measurements. This calculator is for educational purposes only and does not provide medical advice or substitute for prenatal care.

Understanding the Basics: Due Date Calculation Methods and Pregnancy Timeline

Estimated Due Date (EDD) is the approximate date when a pregnancy is expected to reach full term (around 40 weeks from the start of the last menstrual period). Gestational Age is the age of the pregnancy counted from the first day of the last menstrual period (LMP), even though conception usually occurs about two weeks later. Trimesters divide pregnancy into three periods: first trimester (weeks 0-12), second trimester (weeks 13-27), and third trimester (weeks 28-40).

Common Due Date Calculation Methods

Method	Calculation	Best For
LMP Method	LMP + 280 days (40 weeks)	Regular cycles, known LMP
Conception Date	Conception + 266 days (38 weeks)	Known conception date
IVF Transfer	Transfer date + gestational age	IVF pregnancies
Ultrasound	Fetal measurements	Most accurate, first trimester

Pregnancy Trimesters

Pregnancy is divided into three trimesters:

First Trimester: Weeks 0-12. Early development, many changes happening rapidly. This is when most major organs and body systems form.
Second Trimester: Weeks 13-27. Often called the "honeymoon period" of pregnancy, when many people feel their best. Baby grows rapidly, and movement is often felt.
Third Trimester: Weeks 28-40. Final growth and preparation for birth. Baby gains weight, and the body prepares for delivery.

These divisions are helpful for understanding pregnancy progress and when certain tests, screenings, and milestones typically occur. However, individual experiences can vary significantly.

Step-by-Step Guide: How to Use This Calculator

Step 1: Select Dating Method
Choose how you want to calculate your due date: Last Menstrual Period (LMP), Conception Date, IVF Transfer Date, or Known Due Date from Clinician. The LMP method is the most common and works well if you have regular cycles and know your LMP. The conception date method works if you know the exact date of conception. The IVF method is for pregnancies from in vitro fertilization. The known due date option lets you enter a due date provided by your healthcare provider.

Step 2: Enter Your Last Menstrual Period (LMP Method)
If using the LMP method, enter the first day of your last menstrual period. This is the date your period started, not when it ended. Accurate LMP ensures accurate due date calculation. If you're not sure of your LMP, the calculator's estimate may be less accurate, and your healthcare provider will likely use ultrasound measurements instead.

Step 3: Enter Your Cycle Length (Optional)
If your menstrual cycle is longer or shorter than the standard 28 days, enter your average cycle length. This helps the calculator adjust the due date calculation. If you have irregular cycles, the LMP method may be less accurate, and ultrasound dating is often more reliable.

Step 4: Enter Conception Date (Conception Method)
If using the conception date method, enter the exact date of conception. This is typically about 14 days after the first day of your LMP, but can vary based on cycle length and ovulation timing. If you're not sure of your conception date, the LMP method is often easier to use.

Step 5: Enter IVF Transfer Information (IVF Method)
If using the IVF method, enter your transfer date and embryo information (day 3, day 5, or day 6 embryo). The calculator uses the known gestational age at transfer to calculate the due date. Your fertility clinic will provide the most accurate due date based on their specific protocols and any early ultrasound measurements.

Step 6: Enter Known Due Date (Known Due Date Method)
If your healthcare provider has already given you a due date (especially one based on ultrasound), you can enter it here. The calculator will use this date to calculate your current gestational age, trimester ranges, and pregnancy timeline. Your healthcare provider's due date should always take priority over calculator estimates.

Step 7: Answer Health Questions (Optional but Important)
Answer questions about your pregnancy: multiple pregnancy (twins, etc.), high-risk pregnancy. These help the calculator provide appropriate warnings. Multiple pregnancies may have different due dates and require specialized monitoring. High-risk pregnancies require close monitoring and specialized care.

Step 8: Calculate Due Date and Timeline
Click the "Calculate" button. The calculator: (1) Calculates your estimated due date based on the method you selected. (2) Computes your current gestational age in weeks and days. (3) Determines which trimester you're in. (4) Generates trimester ranges (start and end dates for each trimester). (5) Creates a pregnancy timeline with key milestones. (6) Displays results with visual charts. (7) Shows warnings about accuracy and limitations.

Step 9: Interpret Results in Context
Review the results: estimated due date, current gestational age, trimester ranges, and pregnancy timeline. Remember that these are mathematical estimates based on the dates you entered—they assume a standard 40-week pregnancy and don't account for individual variations. Your actual due date may differ based on ultrasound measurements, medical factors, and other considerations. Consider results alongside other factors: your healthcare provider's due date, ultrasound measurements, and your medical history. If you have concerns, discuss results with your healthcare provider for personalized interpretation.

Formulas and Behind-the-Scenes Logic

This calculator uses simple calendar math to estimate due dates and calculate pregnancy timelines. Here's how it works:

LMP Method (Naegele's Rule)

The most common method adds 280 days (40 weeks) to the first day of the last menstrual period:

Due Date = LMP + 280 days

Due Date = LMP + 40 weeks

Example: LMP = January 1, 2025. Due Date = January 1, 2025 + 280 days = October 8, 2025 (approximately 40 weeks later).

Cycle Length Adjustment: If your cycle length differs from 28 days, the calculator adjusts:

Adjusted LMP = LMP + (Cycle Length − 28 days)

Example: LMP = January 1, 2025, cycle length = 35 days. Adjusted LMP = January 1 + (35 − 28) = January 8, 2025. Due Date = January 8, 2025 + 280 days = October 15, 2025.

Conception Date Method

If you know the conception date, the calculator estimates LMP first, then adds 280 days:

Estimated LMP = Conception Date − 14 days

Due Date = Estimated LMP + 280 days

Example: Conception Date = January 15, 2025. Estimated LMP = January 15 − 14 = January 1, 2025. Due Date = January 1 + 280 days = October 8, 2025.

IVF Transfer Date Method

For IVF pregnancies, the gestational age at transfer is known, so the calculator works backwards to estimate LMP:

Estimated LMP = Transfer Date − Gestational Age at Transfer

Due Date = Estimated LMP + 280 days

Example: Transfer Date = January 20, 2025, Day 5 embryo (gestational age ≈ 19 days). Estimated LMP = January 20 − 19 = January 1, 2025. Due Date = January 1 + 280 days = October 8, 2025.

Gestational Age Calculation

Current gestational age is calculated from the reference date (usually today):

Gestational Age (days) = Reference Date − LMP Equivalent Date

Example: LMP = January 1, 2025, Reference Date = March 15, 2025. Gestational Age = March 15 − January 1 = 73 days = 10 weeks 3 days.

Trimester Calculation

Trimesters are calculated based on gestational age:

First Trimester: Weeks 0-12 (LMP to LMP + 84 days)

Second Trimester: Weeks 13-27 (LMP + 85 days to LMP + 189 days)

Third Trimester: Weeks 28-40 (LMP + 190 days to LMP + 280 days)

Example: LMP = January 1, 2025. First Trimester = January 1 to March 26, 2025. Second Trimester = March 27 to July 9, 2025. Third Trimester = July 10 to October 8, 2025.

Complete Worked Example

Setup: LMP = January 1, 2025, Reference Date = March 15, 2025, standard 28-day cycle.

Calculate Due Date:

LMP = January 1, 2025
Due Date = January 1 + 280 days = October 8, 2025

Calculate Gestational Age:

Gestational Age = March 15 − January 1 = 73 days = 10 weeks 3 days

Determine Trimester:

10 weeks 3 days falls in First Trimester (weeks 0-12)
First Trimester: January 1 to March 26, 2025
Second Trimester: March 27 to July 9, 2025
Third Trimester: July 10 to October 8, 2025

Results: Your estimated due date is October 8, 2025. You are currently 10 weeks 3 days pregnant, in the First Trimester. These are mathematical estimates—your actual due date may differ based on ultrasound measurements and individual factors.

Practical Use Cases: Real-World Scenarios

Here are detailed scenarios showing how different people might use this pregnancy due date calculator to understand pregnancy timelines:

1. Student Learning About Pregnancy

Alex, a 22-year-old college student, wants to understand how due dates are calculated. They enter: LMP January 1, 2025, standard 28-day cycle. The calculator shows: due date October 8, 2025, current gestational age 10 weeks 3 days (as of March 15), First Trimester. They see that due dates are calculated by adding 280 days to LMP and that pregnancy is counted from LMP, not conception. They use this information to understand that due dates are estimates and that ultrasound dating is often more accurate.

2. Professional Planning Prenatal Care

Maria, a 30-year-old expecting mother, wants to plan her prenatal care schedule. She enters: LMP January 1, 2025, standard cycle. The calculator shows: due date October 8, 2025, trimester ranges, and key milestones. She sees that First Trimester ends around March 26, Second Trimester runs from March 27 to July 9, and Third Trimester runs from July 10 to October 8. She uses this information to plan prenatal appointments and understand when certain tests and screenings typically occur, while recognizing that her healthcare provider's due date should take priority.

3. Researcher Studying Pregnancy Dating

Dr. Johnson is researching how different dating methods compare. They use the calculator to compute due dates for various LMP dates, conception dates, and IVF transfer dates. They find that different methods produce different estimates, with variations of a few days to a week. The calculator helps them understand how different methods compare and why ultrasound dating is often more accurate, supporting their research on pregnancy dating methods.

4. Tax Payer Understanding Healthcare Benefits

Robert is evaluating healthcare benefits for pregnancy. He enters: LMP January 1, 2025, standard cycle. The calculator shows: due date October 8, 2025, trimester ranges. He sees that pregnancy spans approximately 40 weeks and is divided into three trimesters. He uses this information to understand the timeline of prenatal care and plan for healthcare costs, while recognizing that individual pregnancies vary.

5. Common Person Tracking Pregnancy Progress

Lisa wants to track her pregnancy progress. She enters: LMP January 1, 2025, standard cycle. The calculator shows: due date October 8, 2025, current gestational age 10 weeks 3 days, First Trimester. She records these estimates and compares them to her healthcare provider's due date. She uses this information to see pregnancy progress over time, while recognizing that these are estimates and that ultrasound dating is often more accurate.

6. Person Using IVF Transfer Date

James is calculating his due date from an IVF transfer. He enters: transfer date January 20, 2025, Day 5 embryo. The calculator shows: estimated LMP January 1, 2025, due date October 8, 2025. He sees that IVF dating uses the known gestational age at transfer to estimate LMP, then adds 280 days. He uses this information to understand his pregnancy timeline, while recognizing that his fertility clinic will provide the most accurate due date based on their protocols and ultrasound measurements.

7. Person Preparing for Healthcare Visit

Sarah wants to prepare for a prenatal visit by understanding her due date. She enters: LMP January 1, 2025, standard cycle. The calculator shows: due date October 8, 2025, current gestational age 10 weeks 3 days, First Trimester. She brings this information to her healthcare provider to discuss, and the provider considers these estimates alongside ultrasound measurements and other factors for comprehensive assessment. The provider explains that ultrasound dating is often more accurate than LMP-based calculations, especially in the first trimester, and provides a refined due date based on ultrasound measurements.

Common Mistakes to Avoid

• Treating Due Dates as Exact Predictions: Many people assume due dates are exact predictions of when their baby will arrive, but they're estimates. Only about 5% of babies are born exactly on their due date. Most babies arrive within a window of about two weeks before or two weeks after the due date. Don't expect your baby to arrive exactly on the due date—use it as a reference point, not a guarantee.

• Ignoring Healthcare Provider's Due Date: Many people use calculator estimates instead of their healthcare provider's due date, especially if it's based on ultrasound measurements. Ultrasound dating, especially in the first trimester, is often more accurate than LMP-based calculations. Don't ignore your provider's due date—it should always take priority over calculator estimates. Your provider considers ultrasound measurements, medical history, and other factors that calculators cannot account for.

• Not Accounting for Cycle Length: Many people use the LMP method without adjusting for cycle length. If your menstrual cycle is longer or shorter than 28 days, LMP-based calculations may be less accurate. Don't ignore cycle length—if your cycle differs from 28 days, enter your average cycle length for more accurate estimates. If you have irregular cycles, ultrasound dating is often more reliable.

• Using Uncertain LMP Dates: Many people use uncertain or estimated LMP dates, which reduces accuracy. If you're not sure of your LMP, the calculator's estimate may be less accurate. Don't use uncertain dates—if you're not sure of your LMP, your healthcare provider will likely use ultrasound measurements to determine your due date, which is more accurate. Consider using the "Known Due Date" option if your provider has already given you a due date.

• Ignoring Multiple Pregnancies: Many people use standard due date calculations for multiple pregnancies (twins, triplets), but multiple pregnancies may have different due dates and often deliver earlier than singleton pregnancies. Don't ignore multiple pregnancies—if you're expecting multiples, always follow your healthcare provider's due date and recommendations, as they require specialized monitoring.

• Not Seeking Medical Attention for Concerning Symptoms: Many people use due date calculators to track pregnancy but don't seek medical attention for concerning symptoms. Due date calculators cannot assess pregnancy health, fetal development, or complications. Don't ignore concerning symptoms—if you experience severe abdominal pain, heavy bleeding, decreased fetal movement, or other concerning symptoms, seek immediate medical attention. This calculator is for educational purposes only and does not provide medical advice.

• Making Medical or Treatment Decisions Based on Calculator Results: Never make medical decisions, change medications, or alter treatment plans based solely on due date calculator results. These are mathematical estimates, not medical or clinical assessments. Healthcare and treatment decisions should be made by qualified professionals who consider your full medical history, current health status, ultrasound measurements, and other factors. Always consult healthcare professionals before making health or treatment decisions.

Advanced Tips & Strategies

• Use Your Healthcare Provider's Due Date: Your healthcare provider's due date, especially if based on ultrasound measurements, should always take priority over calculator estimates. Ultrasound dating, especially in the first trimester, is often more accurate than LMP-based calculations because it doesn't depend on knowing your exact LMP or cycle length. If your provider has given you a due date, use the "Known Due Date" option in the calculator to track your pregnancy timeline based on that date.

• Account for Cycle Length: If your menstrual cycle is longer or shorter than 28 days, enter your average cycle length for more accurate LMP-based calculations. Longer cycles (35+ days) may result in later due dates, while shorter cycles (21-25 days) may result in earlier due dates. However, if you have irregular cycles, ultrasound dating is often more reliable than LMP-based calculations.

• Understand Due Date Variability: Due dates are estimates, not exact predictions. Only about 5% of babies are born exactly on their due date. Most babies arrive within a window of about two weeks before or two weeks after the due date. Don't stress if your baby doesn't arrive exactly on the due date—this is normal and expected. Use the due date as a reference point for planning, not a guarantee.

• Track Pregnancy Progress: Use the calculator to track your pregnancy progress over time by comparing gestational age and trimester information. The calculator shows your current gestational age, which trimester you're in, and key pregnancy milestones. However, remember that these are estimates based on the dates you enter, and your actual progress may differ based on ultrasound measurements and individual factors.

• Plan Prenatal Care: Use trimester ranges to plan prenatal care appointments and understand when certain tests and screenings typically occur. First trimester screenings usually occur between weeks 10-13, second trimester screenings between weeks 15-20, and third trimester monitoring becomes more frequent. However, always follow your healthcare provider's recommendations for prenatal care, as they consider your individual circumstances.

• Consider Multiple Pregnancies: If you're expecting multiples (twins, triplets), multiple pregnancies may have different due dates and often deliver earlier than singleton pregnancies. Always follow your healthcare provider's due date and recommendations for multiple pregnancies, as they require specialized monitoring and care. The calculator provides warnings for multiple pregnancies, but your provider's guidance should always take priority.

• Discuss Results with Healthcare Professionals: Bring due date and pregnancy timeline results to prenatal visits to discuss with your healthcare provider. They can interpret results in context of your medical history, current health status, ultrasound measurements, and other factors. Healthcare professionals can help you understand what these dates mean for you personally and recommend appropriate actions, including adjustments to due dates based on ultrasound measurements if needed.

Pregnancy Timeline Benchmarks: Understanding Typical Milestones

While pregnancy experiences vary significantly by individual, here are general benchmarks to help you understand typical pregnancy milestones:

Week	Milestone	Trimester
4-6 weeks	Positive pregnancy test, early development	First
8-12 weeks	First trimester screening, major organs form	First
16-20 weeks	Anatomy scan, feel movement	Second
24-28 weeks	Viability milestone, glucose screening	Second
32-36 weeks	Growth scans, preparation for birth	Third
37-40 weeks	Full term, delivery window	Third

Key Insight: Pregnancy experiences vary significantly by individual, health, medical conditions, and other factors. These benchmarks are general guidelines and don't account for individual factors. Only about 5% of babies are born exactly on their due date—most arrive within a two-week window before or after. Ultrasound dating, especially in the first trimester, is often more accurate than LMP-based calculations. The calculator shows these relationships to help you understand pregnancy timelines, but individual results vary significantly. Focus on your healthcare provider's due date and recommendations rather than comparing to others.

Limitations & Assumptions: What This Calculator Doesn't Include

This calculator uses simplified assumptions to estimate due dates using simple calendar math. It does not account for many real-world complexities:

• Individual Variation: Every pregnancy is unique. Some babies develop faster or slower than average, and pregnancy length can vary. The calculator assumes a standard 40-week (280-day) pregnancy, but actual pregnancy length can vary. Only about 5% of babies are born exactly on their due date—most arrive within a two-week window before or after. The calculator cannot account for individual variation.

• Cycle Length and Irregularity: The calculator can adjust for cycle length, but if you have irregular cycles, LMP-based calculations may be less accurate. Ultrasound dating is often more reliable for irregular cycles because it doesn't depend on knowing your exact LMP or cycle length. The calculator cannot fully account for cycle irregularity.

• Uncertainty About Dates: If you're not sure of your LMP or conception date, the calculator's estimate may be less accurate. Ultrasound dating is often more accurate when dates are uncertain. The calculator cannot verify the accuracy of the dates you enter.

• Multiple Pregnancies: Twins, triplets, and other multiple pregnancies may have different due dates and often deliver earlier than singleton pregnancies. The calculator provides warnings for multiple pregnancies, but it cannot fully account for the unique characteristics of multiple pregnancies. Always follow your healthcare provider's due date and recommendations for multiple pregnancies.

• Medical Factors: Some medical conditions, complications, or risk factors may affect pregnancy length or require specialized monitoring. The calculator cannot account for medical factors. If you have a high-risk pregnancy or medical conditions, always follow your healthcare provider's due date and recommendations.

• Ultrasound Dating: The calculator does not perform ultrasound measurements or use ultrasound data. Ultrasound dating, especially in the first trimester, is often more accurate than LMP-based calculations because it measures fetal size directly. Healthcare providers often use early ultrasound to refine due dates, which can differ from calculator estimates. The calculator cannot replace ultrasound dating.

• Not a Medical Test or Diagnosis: This calculator is not a medical test, pregnancy health assessment, or diagnosis. It provides mathematical estimates based on simple calendar math. Medical evaluation, ultrasound examinations, and other professional assessments are needed to assess pregnancy health, fetal development, and determine appropriate due dates.

• Not a Substitute for Prenatal Care: This calculator is not a substitute for prenatal care, medical advice, or treatment. It provides educational estimates based on simple math. Prenatal care should be provided by qualified healthcare professionals who consider your complete medical history, current health status, ultrasound measurements, and other factors.

Important Note: This calculator is for educational purposes only and does not provide medical advice, diagnose pregnancy health, or substitute for prenatal care. Due date estimates are rough approximations based on simple calendar math and may not match your actual due date, especially if based on ultrasound measurements. Real pregnancy dating involves many factors this tool doesn't model, including individual variation, cycle length and irregularity, uncertainty about dates, multiple pregnancies, medical factors, and ultrasound measurements. Health and pregnancy involve many factors beyond due dates, including overall health, nutrition, prenatal care, medical conditions, and fetal development. Always consult qualified healthcare professionals for accurate due dates (especially those based on ultrasound), prenatal care recommendations, and guidance on pregnancy-related decisions. If you experience severe abdominal pain, heavy bleeding, decreased fetal movement, or other concerning symptoms, seek immediate medical attention. This calculator is not a medical test, pregnancy health assessment, or substitute for professional medical care.

Sources & References

The information in this calculator is based on established obstetric guidelines and research from authoritative health organizations. For more detailed information about pregnancy due dates and prenatal care, please refer to these trusted sources:

American College of Obstetricians and Gynecologists (ACOG): How Your Fetus Grows During Pregnancy – Professional guidelines on pregnancy dating and fetal development.
Centers for Disease Control and Prevention (CDC): Pregnancy – Comprehensive information on pregnancy health and prenatal care.
National Institutes of Health (NIH): Pregnancy Information – Research-based information on pregnancy and fetal development.
March of Dimes: Pregnancy Week by Week – Trusted resource for pregnancy information and support.

Note: This calculator uses Naegele's rule (adding 280 days to the first day of the last menstrual period), which is a standard method for estimating due dates. Ultrasound dating, especially in the first trimester, is generally more accurate for pregnancy dating.

Frequently Asked Questions

Common questions about due dates, pregnancy timelines, and using this calculator.

How accurate are due date calculators?

Due date calculators provide rough estimates based on simple calendar math. They can be helpful for general awareness, but they are not as accurate as ultrasound-based dating performed by healthcare providers. Many factors can affect accuracy, including cycle length, uncertainty about dates, and individual variations. Only about 5% of babies are born exactly on their due date—most arrive within a two-week window before or after. Healthcare providers often use early ultrasound measurements (especially in the first trimester) to refine due dates, which can be more accurate than LMP-based calculations alone. This calculator is for educational purposes only and should not replace your healthcare provider's due date, especially if it's based on ultrasound measurements.

Why is my doctor's due date different from this one?

There are several reasons why your healthcare provider's due date might differ from a calculator estimate: (1) Your provider may have used early ultrasound measurements, which can be more accurate than LMP-based calculations, especially if your cycle length is irregular or uncertain. Ultrasound dating measures fetal size directly and doesn't depend on knowing your exact LMP or cycle length. (2) Your provider considers your complete medical history, physical examination findings, and any complications. (3) Different calculation methods (LMP, conception date, IVF, ultrasound) can produce slightly different estimates, often varying by a few days to a week. Your healthcare provider's due date should always take priority over calculator estimates. This tool is for educational awareness only.

Can this tool tell me if my pregnancy is healthy?

No. This calculator only provides simple calendar-based date estimates. It cannot assess pregnancy health, fetal development, viability, or any medical conditions. It cannot diagnose complications, predict outcomes, or provide medical reassurance. Pregnancy health and fetal development are assessed through prenatal care, including physical examinations, ultrasounds, blood tests, and other medical evaluations performed by healthcare providers. If you have concerns about your pregnancy health, symptoms (such as severe abdominal pain, heavy bleeding, decreased fetal movement), or fetal development, please discuss them with your healthcare provider immediately. This tool is for educational purposes only and does not provide medical advice or diagnosis.

What if I'm not sure of my LMP?

If you're not sure of your last menstrual period (LMP), the calculator's estimate may be less accurate. In this case, your healthcare provider will likely use early ultrasound measurements to determine your due date, which can be more accurate than LMP-based calculations when the LMP is uncertain. Ultrasound dating doesn't depend on knowing your exact LMP or cycle length—it measures fetal size directly. If you're using this calculator and are uncertain about your LMP, consider using the 'Known Due Date (from clinician)' option if your provider has already given you a due date, or wait until you have an ultrasound-based due date from your provider. This tool is for educational awareness only.

How does IVF dating work compared to LMP dating?

IVF pregnancies have a known transfer date and gestational age at transfer, which makes dating more precise than LMP-based calculations. For IVF, the gestational age at transfer depends on the embryo stage (day 3, day 5, or day 6) and whether it was a fresh or frozen transfer. Day 5 embryos (blastocysts) typically have a gestational age of about 19 days at transfer, while day 3 embryos have a gestational age of about 16 days. The calculator works backwards from the transfer date using the known gestational age at transfer to estimate an LMP-equivalent date, then adds 280 days to get the due date. However, your fertility clinic or healthcare provider will provide the most accurate due date based on their specific protocols and any early ultrasound measurements. This calculator is for educational purposes only and should not replace your provider's due date.

What if my cycle is longer or shorter than 28 days?

If your menstrual cycle is longer or shorter than the standard 28 days, you can enter your average cycle length in the calculator for more accurate LMP-based calculations. Longer cycles (35+ days) may result in later due dates, while shorter cycles (21-25 days) may result in earlier due dates. The calculator adjusts the LMP date based on your cycle length before calculating the due date. However, if you have irregular cycles, LMP-based calculations may still be less accurate, and ultrasound dating is often more reliable. Ultrasound dating doesn't depend on cycle length—it measures fetal size directly. If you have irregular cycles, your healthcare provider will likely use ultrasound measurements to determine your due date.

Can I use this for multiple pregnancies (twins, triplets)?

The calculator can provide general estimates for multiple pregnancies, but multiple pregnancies may have different due dates and often deliver earlier than singleton pregnancies. Twins typically deliver around 36-37 weeks, while triplets may deliver even earlier. The calculator provides warnings for multiple pregnancies, but it cannot fully account for the unique characteristics of multiple pregnancies, which require specialized monitoring and care. Always follow your healthcare provider's due date and recommendations for multiple pregnancies, as they consider the specific needs of multiple pregnancies, including more frequent monitoring, potential complications, and delivery planning. This calculator is for educational purposes only and should not replace your provider's guidance for multiple pregnancies.

What percentage of babies are born on their due date?

Only about 5% of babies are born exactly on their due date. Most babies (about 80%) are born within a two-week window before or after the due date (between 38 and 42 weeks). About 10% of babies are born before 37 weeks (preterm), and about 10% are born after 42 weeks (post-term). Due dates are estimates, not exact predictions, and many factors can affect when labor begins, including individual variation, medical factors, and natural variation in pregnancy length. Don't stress if your baby doesn't arrive exactly on the due date—this is normal and expected. Use the due date as a reference point for planning, not a guarantee. Your healthcare provider will monitor your pregnancy and discuss delivery timing based on your individual circumstances.

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