BMR Calculator
Basal metabolic rate is what your body burns doing nothing at all — keeping your heart beating, your brain running and your temperature stable. It is the foundation of every calorie target, and this calculator uses the Mifflin-St Jeor equation, the most accurate of the common formulas for the general population.
Inputs
Result
1,649 kcal/day
Maintenance at light activity ≈ 2,267 kcal
How it works
BMR = 10w + 6.25h − 5a + s
How the bmr calculator works
Mifflin-St Jeor for men: BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age + 5. For women the final constant is −161.
BMR typically accounts for 60–70% of total daily energy expenditure; activity and digestion make up the rest.
Multiply BMR by an activity factor to get TDEE, the number you actually eat against: 1.2 sedentary through to 1.9 for very heavy training.
Worked example: a 34-year-old man, 180 cm, 84 kg
- 10 × 84 = 840.
- 6.25 × 180 = 1,125.
- 5 × 34 = 170.
- BMR = 840 + 1,125 − 170 + 5 = 1,800 kcal.
- At a moderately active factor of 1.55, TDEE ≈ 2,790 kcal.
Common mistakes to avoid
Eating at BMR to lose weight
BMR is a resting floor, not a diet target. Eating at BMR while active produces an extreme deficit, muscle loss and rebound.
Overstating activity level
Most people who describe themselves as very active are moderately active at best. Choosing too high a factor is the usual reason a diet stalls.
Never recalculating
BMR falls as you lose weight. After 5–8 kg of loss, recalculate or your deficit quietly shrinks to nothing.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is resting energy expenditure; TDEE adds activity, exercise and digestion. TDEE is the number you set calorie targets against.
Which BMR formula is most accurate?
Mifflin-St Jeor for most people. Katch-McArdle is better if you know your body fat percentage, because it works from lean mass.
Can I raise my BMR?
Modestly, by adding muscle — roughly 13 kcal per kg of lean tissue per day. Most of the variation between people is size and genetics.
Does age really lower BMR?
Yes, largely through muscle loss rather than age itself. Resistance training offsets much of the decline.
Why is my measured metabolism different?
Equations carry a 10% error band either way. Use the estimate as a starting point and adjust based on two to three weeks of real weight data.
Related calculators
TDEE Calculator
Total daily energy expenditure from BMR and activity.
Calorie Calculator
Daily calorie needs based on activity level and goal.
Macro Split Calculator
Turn a calorie target into protein, carb and fat grams.
Lean Body Mass Calculator
Estimate fat-free mass using the Boer formula.
Protein Intake Calculator
Daily protein target based on weight and goal.