The calories your body burns at complete rest to keep basic functions running.

BMR vs TDEE — what's the difference?

TDEE is BMR multiplied by an activity factor; it's your total daily burn including movement and exercise.

Which BMR formula is most accurate?

Mifflin–St Jeor is the most accurate for the general population and is the modern default.

How do I use BMR to lose weight?

Estimate TDEE from BMR, then eat below it; a ~500 kcal/day deficit is roughly 0.5 kg (1 lb) a week.

Does BMR decrease with age?

Yes — the equation subtracts calories per year of age, reflecting lower lean mass over time.

BMR Calculator

This BMR calculator uses the Mifflin–St Jeor equation to estimate your basal metabolic rate — the calories your body burns at complete rest. Enter your age, sex, height, and weight to get your number, with the Harris–Benedict estimate alongside it.

What basal metabolic rate is

Basal metabolic rate (BMR) is the energy your body uses at complete rest to keep essential functions running — breathing, circulation, cell repair, and brain activity. It's the single biggest part of most people's daily energy use and the baseline you build a calorie target on.

The Mifflin–St Jeor equation

Using kilograms, centimetres, and years:

Men: BMR = 10·kg + 6.25·cm − 5·age + 5
Women: BMR = 10·kg + 6.25·cm − 5·age − 161

Source: Mifflin MD, St Jeor ST, et al. (1990), the equation the Academy of Nutrition and Dietetics recommends for healthy adults.

Worked example

A 30-year-old man, 170 lb (77.1 kg) and 5'10" (177.8 cm): BMR = 10·77.1 + 6.25·177.8 − 5·30 + 5 = 1,737 kcal/day. The revised Harris–Benedict equation gives ~1,804 kcal/day for the same person.

BMR vs TDEE: activity multipliers

Your total daily energy expenditure (TDEE) is BMR multiplied by an activity factor. Pick the row that matches your week:

Activity level	Multiplier	Typical week
Sedentary	×1.2	little or no exercise
Light	×1.375	exercise 1–3 days/week
Moderate	×1.55	exercise 3–5 days/week
Very active	×1.725	exercise 6–7 days/week
Athlete	×1.9	hard daily training / physical job

For a full TDEE and macro breakdown, use the TDEE / Calorie Calculator on our home page.

Mifflin–St Jeor vs Harris–Benedict

The Harris–Benedict equation (1919, revised 1984) was the long-time standard but tends to overestimate BMR slightly for modern body compositions. Mifflin–St Jeor, derived in 1990, is more accurate across a wider population and is now the default. If you know your body-fat percentage, the Katch–McArdle formula (which works from lean body mass) can be more accurate for very lean or very muscular people.

Frequently asked questions

What is BMR?: The calories your body burns at complete rest to keep basic functions running.
BMR vs TDEE — what's the difference?: TDEE is BMR multiplied by an activity factor; it's your total daily burn including movement and exercise.
Which BMR formula is most accurate?: Mifflin–St Jeor is the most accurate for the general population and is the modern default.
How do I use BMR to lose weight?: Estimate TDEE from BMR, then eat below it; a ~500 kcal/day deficit is roughly 0.5 kg (1 lb) a week.
Does BMR decrease with age?: Yes — the equation subtracts calories per year of age, reflecting lower lean mass over time.

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Disclaimer. BMR is an estimate for healthy adults; individual metabolism varies. This is not medical or dietetic advice.