BMR Calculator
Calculate your basal metabolic rate with the Mifflin-St Jeor equation. Get your TDEE across five activity levels, calorie targets for your goal, and a macro breakdown.
Your Details
What you get
BMR
Calories your body burns at complete rest, just to maintain organ function.
TDEE Table
Total daily calorie needs across all five activity levels so you can see the full range.
Goal Calories and Macros
Calorie target for weight loss, maintenance, or muscle gain plus a macro breakdown.
TDEE by Activity Level
Calorie Target by Goal
How the BMR Calculator Works
BMR is the number of calories your body burns at rest to keep organs functioning. It accounts for roughly 60-70% of your total daily energy expenditure.
The Mifflin-St Jeor equation, published in 1990, is considered the most accurate formula for estimating BMR in most adults. The revised Harris-Benedict formula is also available as an alternative.
Multiply BMR by an activity factor to get TDEE — your total daily calorie need. From there, adjusting calories up or down moves you toward your goal.
What this calculator gives you
Mifflin-St Jeor — Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Mifflin-St Jeor — Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Enter your stats
Age, sex, height, and weight. Switch between metric and imperial.
Pick activity level
Choose the option that matches your average weekly exercise load.
Get BMR and TDEE
See your base rate plus TDEE at every activity multiplier at once.
Set your goal
Click a goal card — lose, maintain, or gain — and get your calorie target with macros.
Questions About the BMR Calculator
BMR is the number of calories your body burns at complete rest to keep basic functions running — breathing, circulation, cell repair. It is the foundation of your calorie budget. Eat less than your TDEE to lose weight; eat more to gain. You cannot change your goal without knowing this number first.
Mifflin-St Jeor is a formula developed in 1990 that uses weight, height, age, and sex to estimate BMR. Research consistently finds it more accurate than older formulas like Harris-Benedict for most modern adults. The American Dietetic Association recommends it as the preferred formula for clinical use.
TDEE stands for Total Daily Energy Expenditure. It is your BMR multiplied by an activity factor that accounts for exercise and movement. This is the number of calories you actually burn each day. Eating at TDEE maintains your weight. A deficit below TDEE leads to weight loss; a surplus leads to gain.
A deficit of 500 kcal/day below TDEE results in roughly 0.5 kg of fat loss per week. A 1000 kcal/day deficit targets about 1 kg/week. However, most guidelines recommend not going below 1200 kcal/day for women or 1500 kcal/day for men without medical supervision, as this risks nutrient deficiencies and muscle loss.
Sedentary suits a desk job with minimal movement. Lightly active fits 1-3 days of light exercise. Moderately active fits 3-5 days of moderate gym or cardio work. Very active fits 6-7 hard training days. Extremely active fits athletes with twice-daily training or physically demanding jobs. Most people overestimate their level — if in doubt, go one lower.
The Mifflin-St Jeor formula predicts measured BMR within roughly 10% for most people. It is less accurate for those who are very muscular, very obese, or elderly. The formula treats people with the same height, weight, age, and sex as equivalent — it cannot account for differences in muscle mass or metabolic health. Use the result as a starting point, then adjust based on real-world weight change over 2-4 weeks.
Macros are protein, fat, and carbohydrate — the three calorie-containing nutrients. Protein (4 kcal/g) supports muscle retention and satiety. Fat (9 kcal/g) supports hormones and fat-soluble vitamins. Carbs (4 kcal/g) fuel training and brain function. The calculator suggests higher protein splits for weight loss goals and higher carb splits for muscle gain — both to support performance and body composition.