BMR Calculator

How many calories does your body actually burn? This free BMR calculator uses the Mifflin-St Jeor equation to find your basal metabolic rate and daily calorie needs — with targets for losing, maintaining or gaining weight.

How to Use the BMR Calculator

Select your gender, then enter your age, height in centimeters and weight in kilograms — weigh yourself in the morning for the most consistent figure. Now comes the step people get wrong: choose your activity level honestly. A desk job with no exercise is sedentary, even if you feel busy; walking 8,000 steps daily plus three gym sessions is moderate. Overestimating activity is the single biggest reason calorie targets fail.

Press Calculate Calories to see your BMR (what you burn lying still all day), your TDEE (what you actually burn including movement), and ready-made targets for losing or gaining about half a kilo per week. Revisit the calculator every few weeks as your weight changes — your numbers move with it.

BMR Formula (Mifflin-St Jeor)

Developed in 1990 and validated against lab measurements, the Mifflin-St Jeor equation is the most trusted BMR formula available without clinical testing. It weights four factors — body weight, height, age and sex — because larger bodies burn more, and metabolism slows with age:

TDEE then multiplies BMR by an activity factor from 1.2 (sedentary) to 1.9 (very active). The gap matters enormously: the same person can burn 500+ calories more per day just by moving from sedentary to moderately active — roughly the energy in a full Thanksgiving dinner.

Worked Example

A 30-year-old man, 175 cm tall, weighing 75 kg, exercising moderately (3–5 days a week):

Notice the BMR alone (1,699) would be a starvation diet as a daily target — always base your eating on TDEE, the full 2,633.

Your Calorie Targets — The Table Most Calculators Skip

Knowing your TDEE is only half the job; the other half is turning it into a plan. One kilogram of body fat stores roughly 7,700 calories, so a daily deficit or surplus of 500 calories moves the scale about half a kilo per week. Here is how to use any TDEE figure:

Two rules make this work: eat at least 1.6 g of protein per kilo of body weight when dieting to protect muscle, and recalculate your TDEE after every 3–4 kg lost, because a lighter body burns less. Crash targets below BMR backfire — the weight returns with interest.

Limitations

BMR equations estimate an average body; very muscular people will burn more than predicted and very sedentary or elderly people less. The activity multipliers are broad bands, not measurements — two "moderately active" people can differ by hundreds of calories. Medical conditions (thyroid disorders, PCOS, medications like steroids) shift metabolism beyond what any formula captures. This tool is for healthy adults and is informational only, not medical advice — consult a doctor or registered dietitian before starting a serious diet, especially if you are pregnant, diabetic or managing any condition.

BMR is one half of a health log; the other half is what you actually take and do. The BMI chart guide explains what the more famous number really means, and the Medication Tracker keeps the daily schedule — doses, times and refills — as tidy as the calorie maths.

Frequently Asked Questions

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