BMR Calculator
Find how many calories your body burns at rest and each day.
How to use the BMR Calculator
- Select your gender and enter your age.
- Enter your weight and height.
- Choose your typical activity level.
- See your BMR plus your estimated daily calorie needs (TDEE).
Mifflin-St Jeor: BMR = 10×kg + 6.25×cm − 5×age + (5 for men, −161 for women)
About the BMR Calculator
Your basal metabolic rate is the energy your body spends doing nothing at all — running your heart, brain and kidneys while you lie still. This page estimates it with the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men or −161 for women. It then multiplies that by the activity factor you choose to give your TDEE (total daily energy expenditure), plus and minus 500 kcal.
BMR is worth knowing because it is usually the largest single slice of what you burn in a day — far bigger than a gym session. But Mifflin-St Jeor is a regression equation fitted to population data: give it your age, height, weight and sex and it returns the average person with those numbers. It cannot see your muscle mass, thyroid or medication, and two people with identical inputs genuinely differ.
The activity multiplier is the roughest part of the whole calculation — the line between “moderate” and “active” is a judgement call, and it swings the answer by hundreds of calories. Treat the output as a starting point to test against the scale, not a measurement — an estimate, not a substitute for advice from a doctor or dietitian. See the calorie calculator for goal-adjusted targets, or the BMI calculator.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is what you burn at complete rest. TDEE is BMR multiplied by an activity factor — 1.2 for sedentary up to 1.9 for very active — as an estimate of what you burn across a whole day including work, movement and exercise.
Why does another site give me a different BMR?
Because it uses a different equation. Harris-Benedict and Katch-McArdle (which needs a body fat percentage) both return different numbers from Mifflin-St Jeor. None of them is “correct” — they are competing fits to different sample populations.
How accurate is this for me personally?
It gives the average for people who share your age, sex, height and weight. Individual metabolic rates vary around that average. If your weight is not moving the way the number predicts after a few weeks, trust the scale over the formula.
Does it account for muscle mass?
No. Mifflin-St Jeor uses only weight, height, age and sex. Muscle burns more at rest than fat, so a lean, muscular person’s true BMR tends to sit above this estimate.
Is it safe to eat below my BMR?
That is a decision for a doctor or dietitian, not a calculator. This tool knows nothing about your health history, medication or situation.
Guides & articles about this tool
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