One Rep Max Calculator 2025 | 1RM Strength Calculator Free

Understanding One-Rep Max (1RM): A Comprehensive Guide to Strength Estimation

Last updated: December 15, 2025

A one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's a common metric used in strength training to measure absolute strength and to program training loads. Understanding your 1RM helps you design effective strength training programs, set realistic goals, track progress over time, and determine appropriate training intensities. However, it's important to remember that 1RM estimates are rough approximations based on mathematical formulas and may not match your actual performance exactly.

Whether you're a student learning about strength training, a professional evaluating training performance, a researcher studying exercise physiology, a taxpayer understanding health benefits, or a common person interested in strength training, understanding 1RM estimation provides valuable insights. Different formulas (Epley, Brzycki, Lombardi, O'Connor) use different calculations, which is why they produce different estimates. There is no single "correct" formula—they are all rough approximations based on population averages. Understanding these formulas helps you see strength from multiple perspectives, not just a single number.

Our One-Rep Max Strength Calculator helps you estimate your 1RM for common strength exercises using standard formulas. Simply enter the weight you lifted and the number of reps you completed, and the calculator automatically computes 1RM estimates using multiple formulas (Epley, Brzycki, Lombardi, O'Connor) and shows the average. You can also see a percentage table showing approximate weights for different percentages of your 1RM (useful for program design). The calculator works with both metric and US units, shows results in kilograms and pounds, and provides visual charts.

This tool is perfect for anyone who wants to understand 1RM estimation, see how different formulas compare, design training programs, and make informed decisions about strength training. By calculating 1RM from sub-maximal sets, you can estimate strength without the risks and recovery demands of testing a true 1RM. Remember, these are educational estimates based on mathematical formulas—individual results may vary significantly. Always prioritize proper form, use appropriate safety equipment, and consult qualified professionals before attempting heavy lifts, especially if you have injuries, medical conditions, or are new to strength training. This calculator is for educational purposes only and does not provide medical or fitness advice.

Understanding the Basics: One-Rep Max and Common Formulas

One-Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's used to measure absolute strength and program training loads. Instead of testing a true 1RM (which requires proper preparation, safety equipment, and carries injury risk), many people estimate 1RM using sub-maximal sets (lighter weights with multiple reps) and mathematical formulas.

Common 1RM Estimation Formulas

Formula	Calculation	Best For
Epley	Weight × (1 + Reps/30)	General use, 1-10 reps
Brzycki	Weight × (36/(37-Reps))	1-10 reps, most accurate
Lombardi	Weight × Reps^0.1	Power-based exercises
O'Connor	Weight × (1 + 0.025 × Reps)	Conservative estimate

Why Estimate Instead of Test?

Testing a true 1RM requires: proper warm-up and preparation, safety equipment (spotters, safety bars), risk of injury if form breaks down, time and energy that could be used for training, and recovery time needed after a max attempt. For these reasons, many people estimate their 1RM using sub-maximal sets and formulas, allowing them to get a rough idea of strength without the risks and recovery demands of actually testing a true 1RM.

Common Uses of 1RM Estimates

Program Design: Some training programs use percentages of 1RM to prescribe training loads (e.g., "lift 80% of your 1RM for 5 reps")
Progress Tracking: Estimating 1RM over time can show strength improvements without needing to test a true max frequently
Goal Setting: Having an estimated 1RM can help set realistic strength goals

However, it's important to remember that these are estimates, not guarantees. Actual performance depends on many factors beyond what formulas can account for.

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

Step 1: Select Measurement System
Choose between metric (kilograms) or US units (pounds). The calculator works with both systems and automatically converts between them. Select the system you're most comfortable with or that matches your gym equipment.

Step 2: Enter the Weight You Lifted
Enter the weight you lifted in your sub-maximal set. For metric: Enter weight in kilograms (e.g., 100 kg). For US units: Enter weight in pounds (e.g., 220 lbs). This should be the weight you lifted with proper form for the number of reps you completed. Accurate weight ensures accurate 1RM estimates.

Step 3: Enter the Number of Reps
Enter the number of reps you completed with that weight. For best accuracy, use sets with 1-10 reps. Formulas become less accurate with higher rep counts (above 12 reps), and very high rep sets (20+ reps) may produce unreliable estimates. If you completed 1 rep, the estimated 1RM should be close to the weight lifted.

Step 4: Enter Your Age (Optional)
Enter your age in years. While age doesn't directly affect the calculation, the calculator uses it for context and warnings. These formulas are primarily designed for adults (16+), and results may be less accurate for children, adolescents, or older adults (70+).

Step 5: Select Your Experience Level (Optional)
Select your experience level: beginner, intermediate, or advanced. This helps the calculator provide appropriate warnings and context. Beginners should focus on learning proper technique before attempting heavy loads.

Step 6: Select Formulas to Use
Choose which formulas to calculate: Epley, Brzycki, Lombardi, O'Connor, and/or average of selected. Different formulas produce different estimates, and seeing multiple formulas gives you a better perspective. The calculator can compute all formulas and show the average.

Step 7: Calculate 1RM
Click the "Calculate 1RM" button. The calculator: (1) Computes 1RM estimates using selected formulas. (2) Calculates the average of selected formulas if requested. (3) Generates a percentage table showing approximate weights for different percentages of 1RM (50%, 60%, 70%, 80%, 85%, 90%, 95%). (4) Displays results with visual charts. (5) Shows warnings about accuracy and limitations.

Step 8: Interpret Results in Context
Review the results: 1RM estimates from each formula, average 1RM, and percentage table. Remember that these are mathematical estimates based on the numbers you entered—they assume proper form, adequate warm-up, and fresh condition. Your actual 1RM may differ based on individual factors. Consider results alongside other factors: technique, fitness level, fatigue, injuries, and equipment. If you have concerns, discuss results with a healthcare professional or qualified coach for personalized interpretation.

Formulas and Behind-the-Scenes Logic

This calculator uses mathematical formulas to estimate 1RM from sub-maximal sets. Here's how it works:

Epley Formula

One of the most commonly used formulas:

1RM = Weight × (1 + Reps / 30)

Example: Weight 100 kg, 8 reps. 1RM = 100 × (1 + 8/30) = 100 × 1.267 = 126.7 kg (279 lbs).

Brzycki Formula

Often considered one of the most accurate for 1-10 reps:

1RM = Weight × (36 / (37 - Reps))

Example: Weight 100 kg, 8 reps. 1RM = 100 × (36 / (37 - 8)) = 100 × (36 / 29) = 100 × 1.241 = 124.1 kg (274 lbs).

Lombardi Formula

Uses a power function, often used for power-based exercises:

1RM = Weight × Reps^0.1

Example: Weight 100 kg, 8 reps. 1RM = 100 × 8^0.1 = 100 × 1.231 = 123.1 kg (271 lbs).

O'Connor Formula

Provides a more conservative estimate:

1RM = Weight × (1 + 0.025 × Reps)

Example: Weight 100 kg, 8 reps. 1RM = 100 × (1 + 0.025 × 8) = 100 × 1.2 = 120 kg (265 lbs).

Average of Selected Formulas

The calculator can compute the average of selected formulas:

Average 1RM = (Epley + Brzycki + Lombardi + O'Connor) ÷ 4

Example: Epley = 126.7 kg, Brzycki = 124.1 kg, Lombardi = 123.1 kg, O'Connor = 120 kg. Average = (126.7 + 124.1 + 123.1 + 120) ÷ 4 = 123.5 kg (272 lbs).

Percentage Table Calculation

The calculator generates a percentage table showing approximate weights for different percentages of 1RM:

Weight at X% = 1RM × (X / 100)

Approximate rep ranges are estimated based on typical strength curves

Example: 1RM = 100 kg. Weight at 80% = 100 × 0.80 = 80 kg (approximately 5-8 reps). Weight at 70% = 100 × 0.70 = 70 kg (approximately 8-10 reps).

Complete Worked Example

Setup: You bench pressed 100 kg for 8 reps and want to estimate your 1RM.

1RM Calculations:

Epley: 100 × (1 + 8/30) = 100 × 1.267 = 126.7 kg (279 lbs)
Brzycki: 100 × (36/(37-8)) = 100 × 1.241 = 124.1 kg (274 lbs)
Lombardi: 100 × 8^0.1 = 100 × 1.231 = 123.1 kg (271 lbs)
O'Connor: 100 × (1 + 0.025 × 8) = 100 × 1.2 = 120 kg (265 lbs)
Average: (126.7 + 124.1 + 123.1 + 120) ÷ 4 = 123.5 kg (272 lbs)

Percentage Table (using average 1RM = 123.5 kg):

95% = 117.3 kg (approximately 1-2 reps)
90% = 111.2 kg (approximately 2-4 reps)
85% = 105.0 kg (approximately 3-6 reps)
80% = 98.8 kg (approximately 5-8 reps)
70% = 86.5 kg (approximately 8-10 reps)
60% = 74.1 kg (approximately 12-15 reps)
50% = 61.8 kg (approximately 15-20 reps)

Results: Your estimated 1RM ranges from 120-126.7 kg depending on the formula, with an average of 123.5 kg. These are mathematical estimates—your actual 1RM may differ based on individual factors.

Practical Use Cases: Real-World Scenarios

Here are detailed scenarios showing how different people might use this 1RM calculator to understand strength estimation:

1. Student Learning About Strength Training

Alex, a 22-year-old college student, wants to understand their bench press strength. They enter: weight 80 kg, reps 5, experience intermediate. The calculator shows: Epley 93.3 kg, Brzycki 90.0 kg, Lombardi 89.3 kg, O'Connor 90.0 kg, average 90.7 kg (200 lbs). They see that their estimated 1RM is around 90-93 kg depending on the formula. They use this information to understand that 1RM estimation uses mathematical formulas and that different formulas produce different estimates.

2. Professional Designing Training Program

Maria, a 30-year-old strength trainer, wants to design a training program using percentage-based loading. She enters: weight 100 kg, reps 8, experience advanced. The calculator shows: average 1RM 123.5 kg, and a percentage table showing weights for different percentages. She sees that 80% of 1RM = 98.8 kg (approximately 5-8 reps), which she can use for strength training. She uses this information to design her program, while recognizing that these are estimates and that individual factors affect actual performance.

3. Researcher Studying Strength Formulas

Dr. Johnson is researching how different 1RM formulas compare. They use the calculator to compute 1RM estimates for various weight and rep combinations using different formulas. They find that formulas produce different estimates, with variations of 2-5% for the same input. The calculator helps them understand how different formulas compare and why there's no single "correct" formula, supporting their research on strength estimation methods.

4. Tax Payer Understanding Health Benefits

Robert is evaluating his health to understand potential healthcare costs. He enters: weight 60 kg, reps 10, experience beginner. The calculator shows: average 1RM 72.0 kg (159 lbs). He sees that his estimated 1RM is 72 kg. He uses this information to understand his strength level and motivate strength training to improve health and reduce future healthcare costs.

5. Common Person Tracking Progress

Lisa wants to track her squat strength progress over time. She enters: weight 70 kg, reps 6, experience intermediate. The calculator shows: average 1RM 82.3 kg (181 lbs). She records this estimate and compares it to previous estimates to track progress. She uses this information to see strength improvements over time, while recognizing that these are estimates and that actual performance may vary.

6. Person Using Percentage Table for Training

James wants to use the percentage table to plan his training. He enters: weight 90 kg, reps 5, experience advanced. The calculator shows: average 1RM 105.0 kg, and a percentage table. He sees that 85% of 1RM = 89.3 kg (approximately 3-6 reps), which he can use for strength training. He uses this information to plan training loads, while recognizing that rep ranges are approximate and that individual factors affect actual performance.

7. Person Preparing for Healthcare Visit

Sarah wants to prepare for a healthcare visit by understanding her strength levels. She enters: weight 50 kg, reps 8, experience beginner. The calculator shows: average 1RM 61.3 kg (135 lbs). She brings this information to her healthcare provider to discuss, and the provider considers these estimates alongside other health factors (blood pressure, cholesterol, overall fitness) for comprehensive assessment. The provider explains that these are mathematical estimates and that actual performance depends on many factors beyond simple math, and recommends working with a qualified trainer for proper strength training guidance.

Common Mistakes to Avoid

• Treating Estimates as Guarantees: Many people assume 1RM estimates are guarantees of what they can actually lift, but they're mathematical estimates based on formulas. Don't expect to match estimates exactly—actual 1RM depends on many factors: technique, warm-up, fatigue, injuries, equipment, and how you feel on a given day. Your actual 1RM may be higher or lower than the estimate. Use estimates as general references, not performance guarantees.

• Using High Rep Sets for Estimation: Many people use very high rep sets (15+ reps) to estimate 1RM, but formulas become less accurate with higher rep counts. Don't use high rep sets—formulas are most accurate for 1-10 reps. Very high rep sets (20+ reps) may produce unreliable estimates. For best accuracy, use sets with 1-10 reps.

• Ignoring Form and Technique: Many people use weights lifted with poor form to estimate 1RM, but form breakdown affects accuracy. If your form breaks down during the sub-maximal set, the estimate will be based on suboptimal performance. Don't ignore form—good form is essential for accurate estimates. Always use weights lifted with proper form.

• Not Accounting for Fatigue: Many people use weights lifted when fatigued to estimate 1RM, but fatigue affects accuracy. How you feel on a given day matters—fatigue from previous workouts, lack of sleep, stress, or other factors can significantly affect your ability to lift. Don't use fatigued sets—use weights lifted when fresh and recovered for more accurate estimates.

• Attempting True 1RM Without Proper Preparation: Many people use 1RM estimates to attempt true 1RM lifts without proper preparation, safety equipment, or supervision. Testing a true 1RM requires proper warm-up, safety equipment (spotters, safety bars), and ideally professional supervision. Don't attempt true 1RM without proper preparation—estimates are meant to avoid the need for true 1RM testing. If you do decide to test a true 1RM, ensure you have proper form, adequate warm-up, safety equipment, and professional guidance.

• Using Estimates as Training Plans: Many people use 1RM estimates to create training plans, but the calculator doesn't provide training plans. Training plans should be personalized to your fitness level, goals, schedule, and health status, and should include gradual progression, rest days, and variety. Don't use estimates as training plans—consult qualified coaches or fitness professionals for proper training plans.

• Making Medical or Fitness Decisions Based on Calculator Results: Never make medical decisions, change medications, or alter treatment plans based solely on 1RM calculator results. These are mathematical estimates, not medical or fitness assessments. Healthcare and fitness decisions should be made by qualified professionals who consider your full medical history, current health status, and other factors. Always consult healthcare professionals or qualified coaches before making health or fitness decisions.

Advanced Tips & Strategies

• Use Multiple Formulas for Comparison: Different formulas produce different estimates, and seeing multiple formulas gives you a better perspective. Use all formulas (Epley, Brzycki, Lombardi, O'Connor) and compare results. The average of all formulas often provides a more balanced estimate than any single formula. For example, if formulas range from 120-127 kg, the average (123.5 kg) is a better reference than any single formula.

• Use Appropriate Rep Ranges: For best accuracy, use sets with 1-10 reps. Formulas are most accurate in this range. Avoid using very high rep sets (15+ reps) as accuracy decreases significantly. If you only have high rep data, recognize that estimates may be less reliable. For most accurate estimates, perform a set with 3-8 reps at a weight you can lift with proper form.

• Ensure Proper Form and Fresh Condition: Use weights lifted with proper form when fresh and recovered for more accurate estimates. Don't use weights lifted with poor form or when fatigued—these will produce inaccurate estimates. Perform your test set after adequate warm-up but before fatigue sets in. Good form is essential for accurate estimates.

• Track Progress Over Time: Use 1RM estimates to track progress over time by comparing estimates from similar test sets performed periodically (e.g., monthly). Improving 1RM estimates for the same exercise indicates strength improvement. However, don't expect linear improvement—progress varies based on training, recovery, and other factors. Focus on long-term trends rather than day-to-day variations.

• Use Percentage Table for Program Design: The percentage table shows approximate weights for different percentages of 1RM, which can be useful for program design. For example, 80-85% of 1RM is typically used for strength training (3-6 reps), while 65-75% is used for hypertrophy (8-12 reps). However, recognize that rep ranges are approximate and that individual factors affect actual performance. Use the table as a guide, not a strict prescription.

• Don't Test True 1RM Frequently: Testing a true 1RM is physically and mentally demanding and requires recovery time. Don't test true 1RM frequently—use estimates from sub-maximal sets instead. Most effective training programs don't require knowing your exact 1RM. Estimate 1RM periodically (e.g., monthly) from sub-maximal sets to track progress without the risks and recovery demands of true 1RM testing.

• Discuss Results with Healthcare Professionals or Coaches: Bring 1RM estimates to healthcare visits or coaching consultations to discuss with providers. They can interpret results in context of your medical history, current health status, fitness level, and other factors. Healthcare professionals and coaches can help you understand what these numbers mean for you personally and recommend appropriate actions, including training plans if needed.

1RM Benchmarks: Understanding Typical Strength Levels

While 1RM varies significantly by individual, here are general benchmarks to help you understand typical strength levels. These are rough examples and don't define fitness or health:

Exercise	Beginner (70 kg person)	Intermediate (70 kg person)	Advanced (70 kg person)
Bench Press	50-70 kg (110-154 lbs)	80-100 kg (176-220 lbs)	110-130+ kg (243-287+ lbs)
Squat	60-80 kg (132-176 lbs)	100-130 kg (220-287 lbs)	140-180+ kg (309-397+ lbs)
Deadlift	70-90 kg (154-198 lbs)	120-150 kg (265-331 lbs)	170-220+ kg (375-485+ lbs)

Key Insight: 1RM varies significantly by individual, exercise, body weight, training experience, genetics, and other factors. These benchmarks are general guidelines for a 70 kg person and don't account for individual factors. Heavier people typically have higher 1RM values, and training experience significantly affects strength. The calculator shows these relationships to help you understand strength estimation, but individual results vary significantly. Focus on your own progress rather than comparing to others.

Limitations & Assumptions: What This Calculator Doesn't Include

This calculator uses simplified assumptions to estimate 1RM using mathematical formulas. It does not account for many real-world complexities:

• Individual Strength Curves: Different people have different strength curves. Some people are relatively stronger at lower reps (closer to their 1RM), while others are relatively stronger at higher reps. Formulas use population averages and cannot account for individual differences. Your actual strength curve may differ from what formulas assume.

• Exercise-Specific Differences: Different exercises may have different relationships between sub-maximal reps and 1RM. For example, some exercises (like deadlifts) may have different strength curves than others (like bench press). Formulas don't account for exercise-specific differences. The same formula may be more or less accurate for different exercises.

• Training Status: Well-trained individuals may have different strength curves than beginners. Formulas are based on general population data and may not accurately reflect the specific characteristics of highly trained athletes or complete beginners. Advanced lifters may have different rep-to-1RM relationships than beginners.

• Form and Technique: If your form breaks down during the sub-maximal set, the estimate will be based on suboptimal performance. Good form is essential for accurate estimates, but the calculator cannot verify form quality. Poor form can lead to inaccurate estimates and increased injury risk.

• Fatigue and Recovery: How you feel on a given day matters. Fatigue from previous workouts, lack of sleep, stress, or other factors can significantly affect your ability to lift. The calculator assumes you're fresh and recovered, which may not be the case. Using weights lifted when fatigued will produce inaccurate estimates.

• Injuries and Medical Conditions: If you have injuries, pain, or medical conditions, your safe lifting capacity may be different from what formulas estimate. The calculator cannot account for injuries or medical conditions. Pushing through pain or ignoring injuries to hit a number can cause serious harm. Always prioritize health and safety over hitting a specific weight.

• Equipment and Environment: The equipment you use (barbell, dumbbells, machines), the gym environment, and safety equipment (spotters, safety bars) all affect what weights are safe to attempt. The calculator doesn't account for equipment or environmental factors. Different equipment may affect performance differently.

• Rep Range Accuracy: Formulas are generally most accurate in the 1-10 rep range. As rep counts increase (above 12 reps), accuracy decreases significantly. Very high rep sets (20+ reps) may produce unreliable estimates. The calculator provides warnings for high rep counts, but cannot prevent inaccurate estimates if high reps are used.

• Not a Training Plan or Performance Guarantee: This calculator is not a training plan, coaching program, or guarantee that you can safely lift the estimated weights. It provides mathematical estimates based on formulas. Training plans should be personalized to your fitness level, goals, schedule, and health status, and should include gradual progression, rest days, and variety. Performance depends on many factors beyond simple math.

Important Note: This calculator is for educational purposes only and does not provide medical or fitness advice. 1RM estimates are rough approximations based on mathematical formulas and may not match your actual performance. Real strength testing involves many factors this tool doesn't model, including individual strength curves, exercise-specific differences, training status, form and technique, fatigue and recovery, injuries and medical conditions, and equipment and environment. Health and fitness involve many factors beyond 1RM, including overall physical activity, nutrition quality, sleep, stress management, mental health, and medical history. Always consult qualified healthcare professionals or qualified coaches for personalized training guidance, interpretation of 1RM results, and guidance on health-related decisions, especially if you have health conditions, injuries, or are new to strength training. This calculator is not a training plan, coaching program, or guarantee that you can safely lift the estimated weights. Always prioritize proper form, use appropriate safety equipment (like spotters or safety bars), and consult with qualified professionals before attempting heavy lifts.

Sources & References

The information in this calculator is based on established strength training research and guidelines from authoritative organizations. For more detailed information about strength training and 1RM testing, please refer to these trusted sources:

National Strength and Conditioning Association (NSCA): NSCA.com – Evidence-based resources on strength training and conditioning.
American College of Sports Medicine (ACSM): ACSM.org – Guidelines on resistance training and exercise prescription.
Centers for Disease Control and Prevention (CDC): Physical Activity Guidelines – Recommendations on muscle-strengthening activities.
National Institutes of Health (NIH): Benefits of Strength Training – Research on health benefits of resistance training.

Note: This calculator uses established 1RM estimation formulas (Epley, Brzycki, Lander, Lombardi, O'Conner) that are widely used in strength training. Actual 1RM should be tested under proper supervision with appropriate safety measures.

Frequently Asked Questions

Common questions about one-rep max estimates and strength training.

How accurate are 1RM calculators?

1RM calculators provide rough approximations based on mathematical formulas. Accuracy varies depending on the rep range used (most accurate for 1-10 reps), individual strength curves, exercise type, and training status. Different formulas (Epley, Brzycki, Lombardi, O'Connor) may give slightly different estimates, often varying by 2-5% for the same input. These are educational estimates, not precise measurements. Actual performance can vary significantly from estimates (often by 5-10% or more) due to factors like technique, fatigue, equipment, injuries, and individual differences. For best accuracy, use sets with 3-8 reps performed with proper form when fresh and recovered.

Does this tell me what weight I can actually lift once?

No. This calculator provides mathematical estimates based on formulas, not guarantees of what you can actually lift. Your actual one-rep max depends on many factors that formulas cannot account for: technique, warm-up, fatigue, injuries, equipment, environment, and how you feel on a given day. The estimate is a starting point for understanding strength, but it does not guarantee that you can safely lift that weight. Your actual 1RM may be higher or lower than the estimate, often by 5-10% or more. Always prioritize proper form, use safety equipment (spotters, safety bars), and consult with qualified professionals before attempting heavy lifts.

Which formula is most accurate?

There is no single 'most accurate' formula—different formulas work better for different people, exercises, and rep ranges. Brzycki is often considered one of the most accurate for 1-10 reps, but it's less accurate for higher reps. Epley is widely used and generally reliable for 1-10 reps. Lombardi uses a power function and may work better for power-based exercises. O'Connor provides more conservative estimates. The calculator shows multiple formulas so you can compare results. Many people find the average of all formulas provides a more balanced estimate than any single formula. Individual factors (strength curve, exercise type, training status) affect which formula works best for you.

Should I test my real 1RM in the gym?

Testing a true 1RM should only be done with proper preparation, safety equipment (spotters, safety bars), and ideally under the supervision of a qualified coach or trainer. It's not necessary for most people, especially beginners. Many effective training programs don't require knowing your exact 1RM—estimates from sub-maximal sets are sufficient for program design. Testing a true 1RM is physically and mentally demanding, requires recovery time, and carries injury risk if not done properly. If you do decide to test a 1RM, ensure you have proper form, adequate warm-up, safety equipment, and professional guidance. This calculator is for educational estimates only and does not recommend or encourage testing a true 1RM. Most people should use estimates instead of testing true 1RM.

Can I use this tool to design my entire strength program?

No. This calculator is for educational purposes only and does not provide training programs, coaching, or fitness advice. A proper strength training program should be personalized to your goals, fitness level, schedule, health status, and individual needs. It should include appropriate progression, variety in exercises and rep ranges, rest days, periodization, and consideration of your specific circumstances. The percentage table can be useful for understanding training loads, but it's not a complete training system. For a training program, consult with a qualified coach or trainer who can assess your situation and create a safe, effective plan tailored to your individual needs. This tool provides rough strength estimates, not a complete training system.

What if I have pain or an injury?

If you have pain, injuries, or medical conditions, do not use this calculator to determine what weights to lift. Pain is a signal that something is wrong, and pushing through pain can cause serious harm. The calculator cannot account for injuries or medical conditions, and using it to determine training loads when injured can worsen injuries. Consult with a healthcare professional (doctor, physical therapist) or qualified trainer who understands your specific situation. They can help you determine safe exercises, appropriate loads, modifications, and whether strength training is appropriate for your condition. This calculator is for educational purposes only and does not provide medical or injury advice. Always prioritize health and safety over hitting a specific weight.

How do I use the percentage table for training?

The percentage table shows approximate weights for different percentages of your estimated 1RM, which can be useful for program design. For example, 80-85% of 1RM is typically used for strength training (approximately 3-6 reps), 65-75% for hypertrophy/muscle growth (approximately 8-12 reps), and 50-65% for muscular endurance (approximately 12-20+ reps). However, recognize that rep ranges are approximate and that individual factors affect actual performance. The table is a guide, not a strict prescription. Your actual rep capacity at a given percentage may differ based on exercise, fitness level, fatigue, and other factors. Use the table as a starting point and adjust based on how you feel and your actual performance. For personalized program design, consult with a qualified coach.

Why do different formulas give different results?

Different formulas use different mathematical approaches to estimate 1RM from sub-maximal sets, which is why they produce different estimates. Epley uses a linear relationship (Weight × (1 + Reps/30)), Brzycki uses a ratio (Weight × (36/(37-Reps))), Lombardi uses a power function (Weight × Reps^0.1), and O'Connor uses a conservative multiplier (Weight × (1 + 0.025 × Reps)). Each formula is based on different research and assumptions about how strength relates to rep count. The variation between formulas (often 2-5% for the same input) illustrates that these are estimates, not exact measurements. Some people find it helpful to see the range of estimates, while others prefer to look at the average. The calculator shows all formulas so you can compare and choose what works best for you, or use the average for a more balanced estimate.

Related Health & Benefits Tools

Explore other calculators to help you understand your health metrics, calorie needs, and make informed decisions about your nutrition and well-being.

One-Rep Max Strength Calculator

Enter Your Information