BMR Calculator
Estimate the calories your body burns at rest — plus your daily needs by activity level.
How to use
- Enter your gender, age, height and weight (pick metric or imperial).
- Click Calculate.
- See your BMR and daily calorie needs (TDEE) for five activity levels.
For information only — not medical advice. Consult a healthcare professional for personal guidance.
What Is a BMR Calculator?
Your basal metabolic rate (BMR) is the number of calories your body burns in 24 hours at complete rest — the energy spent just keeping you alive: breathing, circulating blood, maintaining body temperature, and running your brain and organs. It is the largest single piece of your daily energy expenditure, typically 60–70% of everything you burn. This calculator estimates your BMR from your age, gender, height, and weight, then shows what that baseline becomes at several everyday activity levels.
BMR matters because every sensible calorie target starts here. Eating plans, weight-loss deficits, and muscle-gain surpluses are all built by taking BMR, scaling it for activity to get total daily energy expenditure (TDEE), and then adjusting up or down. Guessing your intake without this anchor is how diets end up hundreds of calories off in either direction.
How to Use the BMR Calculator
- Choose your units — metric (kg/cm) or imperial (lbs/in).
- Select your gender, since the estimating equation differs for men and women.
- Enter your age, height, and current body weight.
- Click Calculate to see your BMR and your estimated daily calorie needs at a range of activity levels, from sedentary to very active.
The Mifflin-St Jeor Equation
This calculator uses the Mifflin-St Jeor equation, published in 1990 and repeatedly found in validation studies to be the most accurate of the classic formulas for the general adult population. For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women, the same equation ends with − 161 instead of + 5. Multiplying BMR by an activity factor — roughly 1.2 for sedentary days up to about 1.9 for very heavy training or physical work — converts the resting figure into an estimate of total daily burn.
Tips for Using Your BMR
- Treat the result as a starting estimate, then adjust: if your weight is stable at a given intake for two to three weeks, that intake is your real maintenance level.
- Recalculate after meaningful weight change — a body that weighs 10 kg less genuinely needs fewer calories, even at rest.
- Remember the equation cannot see body composition. Two people of identical weight can differ because muscle tissue burns more at rest than fat tissue.
What is the difference between BMR and RMR?
Resting metabolic rate (RMR) is measured under slightly less strict conditions than BMR — no overnight fast in a lab — so RMR figures usually come out a little higher. In everyday use the two terms are treated as interchangeable, and calculators like this one use BMR equations to estimate resting burn.
How accurate is this calculator?
For most adults the Mifflin-St Jeor equation lands within roughly 10% of a laboratory measurement. Individual variation is real, though — genetics, thyroid function, body composition, and medications all shift true metabolic rate — so use the number as a well-informed estimate, not an exact measurement.
Should I eat exactly my BMR in calories?
No. BMR is what you would burn lying in bed all day; you also move, digest food, and live your life, so your actual daily need (TDEE) is always higher. Eating below your BMR for extended periods is generally discouraged without medical supervision — deficits are normally taken from TDEE, not from BMR.
Does BMR change with age?
Yes. The equation subtracts calories as age rises, reflecting the gradual loss of muscle mass and metabolic slowdown that typically accompany aging. Strength training and staying active can offset part of that decline, which is one reason the same formula gives only an estimate for any individual.