BMR / TDEE and Calorie Needs Calculator

Your body requires energy (calories) every day to function, even when you're completely at rest. Understanding your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) helps you estimate how many calories your body needs to maintain, lose, or gain weight.

What is BMR (Basal Metabolic Rate)?

BMR is the number of calories your body burns at complete rest—lying in bed, doing nothing, in a temperature-controlled environment. It represents the energy needed for essential bodily functions like breathing, circulating blood, regulating body temperature, cell production, brain function, and maintaining organ function.

BMR accounts for approximately 60-75% of your total daily calorie burn. It's influenced by factors like age, sex, height, weight, and body composition (muscle mass vs. fat mass). Generally, men have higher BMRs than women due to typically higher muscle mass, and BMR decreases with age as muscle mass naturally declines.

What is TDEE (Total Daily Energy Expenditure)?

TDEE is your total daily calorie burn, including BMR plus all activity throughout the day. It's calculated by multiplying your BMR by an activity factor that accounts for:

• Sedentary (1.2x): Little or no exercise, desk job
• Light (1.375x): Light exercise 1-3 days/week
• Moderate (1.55x): Moderate exercise 3-5 days/week
• Active (1.725x): Hard exercise 6-7 days/week
• Very Active (1.9x): Very hard exercise or physical job

TDEE represents the calories you need to consume to maintain your current weight. If you eat more than your TDEE, you'll gain weight; if you eat less, you'll lose weight.

How BMR and TDEE Are Calculated

This calculator uses the Mifflin-St Jeor equation, which is considered one of the most accurate BMR formulas for adults. It takes into account your age, sex, height, and weight. The formula is:

TDEE is then calculated by multiplying BMR by your selected activity level multiplier.

BMR and TDEE calculations provide rough estimates, not exact numbers. Many factors can significantly affect your actual calorie needs:

Factors That Can Change Calorie Needs

• Muscle mass: Muscle burns more calories at rest than fat. Two people with the same weight but different body compositions will have different BMRs.
• Medical conditions: Thyroid disorders, diabetes, hormonal imbalances, and other conditions can affect metabolism.
• Pregnancy and breastfeeding: Significantly increase calorie needs (typically 300-500+ extra calories per day).
• Medications: Some medications can increase or decrease metabolism or appetite.
• Genetics: Some people naturally have faster or slower metabolisms.
• Sleep: Poor sleep can affect hormones that regulate appetite and metabolism.
• Stress: Chronic stress can affect cortisol levels and metabolism.
• Age: Metabolism naturally slows with age, but this is partially due to muscle loss, which can be mitigated with strength training.
• Adaptive thermogenesis: Your body may adjust its metabolism in response to prolonged calorie restriction or surplus.

Activity Level Estimates Are Approximate

The activity multipliers used to calculate TDEE are broad categories. Your actual activity level may not fit perfectly into these categories. For example:

• A construction worker might burn more than "very active" suggests
• A weekend warrior who exercises intensely 2 days/week might fall between "light" and "moderate"
• Someone with a desk job but who walks 10,000 steps daily might need a custom estimate

The calculator provides approximate calorie ranges for different goals. These are educational estimates, not personalized meal plans:

Maintain Weight

To maintain your current weight, aim to eat approximately your TDEE. This means consuming roughly the same number of calories you burn each day. Small variations (100-200 calories) are normal and won't significantly affect weight over time.

Gentle Weight Loss

For gradual, sustainable weight loss, the calculator suggests a modest calorie deficit (typically 250-500 calories below TDEE). This generally results in losing about 0.5-1 pound per week. Very low calorie intakes (below 1200-1400 kcal/day for most adults) can be unsafe and may slow metabolism, so the calculator warns if ranges fall too low.

Important: Rapid weight loss (more than 1-2 pounds per week) is often unsustainable and can lead to muscle loss, nutritional deficiencies, and metabolic adaptation. Gradual changes are more likely to be maintained long-term.

Gentle Weight Gain

For gradual weight gain (useful for building muscle, recovering from illness, or underweight individuals), the calculator suggests a modest calorie surplus (typically 250-500 calories above TDEE). This generally results in gaining about 0.5-1 pound per week. Combined with strength training, this can help build muscle rather than just fat.

While BMR and TDEE calculators provide useful estimates, personalized guidance from qualified professionals is essential for:

• Medical conditions: Diabetes, heart disease, kidney disease, and other conditions require specialized nutrition plans
• Pregnancy and breastfeeding: Calorie and nutrient needs are significantly different and change throughout pregnancy and lactation
• Athletes: High-performance athletes may need specialized fueling strategies that go beyond standard TDEE calculations
• Eating disorders: Recovery requires professional supervision and cannot be managed with calorie calculators alone
• Medications: Some medications interact with food or require specific meal timing
• Age considerations: Children, teens, and older adults have different nutritional needs
• Body composition goals: Building muscle while losing fat requires specific strategies beyond simple calorie deficits