How do you calculate BMR?

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. A 60 kg, 165 cm woman of 40: 600 + 1,031 − 200 − 161 = 1,270 kcal a day. Enter your figures above and the working is shown.

What is the difference between BMR and TDEE?

BMR is the energy used at complete rest. TDEE — total daily energy expenditure, also called maintenance calories — adds everything else: moving, working, exercising, digesting. TDEE is BMR times an activity factor from about 1.2 (desk-bound) to 1.9 (hard daily training). The maintenance-calories calculator applies those factors.

Which is more accurate, Mifflin-St Jeor or Harris-Benedict?

Mifflin-St Jeor, in most comparisons on modern adults, which is why the Academy of Nutrition and Dietetics and most calculators use it. Harris-Benedict, even revised, was fitted to a leaner early-20th-century sample and tends to overestimate slightly. Both are shown here so you can see the gap.

Why is a woman's BMR lower than a man's of the same size?

On average women carry a higher share of body fat and less muscle at the same weight and height, and fat tissue uses less energy at rest than muscle. The −161 constant in the women's equation is how the fitted data expressed that difference; it is an average, not a rule for any one person.

Is BMR the same as resting metabolic rate?

Nearly. BMR is measured fasted and at complete rest just after waking; resting metabolic rate is measured under looser conditions and runs a little higher. Mifflin and St Jeor fitted their equation to resting energy expenditure, so it estimates the latter.

BMR Calculator (Mifflin-St Jeor and Harris-Benedict)

Basal metabolic rate from weight, height, age and sex, by the two standard formulas, working shown.

Inputs

Weight(kg)

2 kg300 kg

Height(cm)

50 cm250 cm

Age(years)

2 years100 years

Sex

Formula

Units

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BMR

1649 kcal/day

Formula: Mifflin-St Jeor (1990)
Working (kg, cm): 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1,648.8
The other formula gives: 1696 kcal/day
Per hour: 69 kcal

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What each BMR input means

Weight: Body weight in kg, or pounds in US units. A morning weight before eating is the most repeatable.
Height: Height in cm, or feet and inches in US units, without shoes.
Age: Age in years. Both formulas lower the estimate as age rises.
Sex: Male or female. The formulas were fitted separately: Mifflin-St Jeor adds 5 for men and subtracts 161 for women.
Formula: Mifflin-St Jeor (1990), the usual first choice, or the Roza and Shizgal revision (1984) of Harris-Benedict for comparison.
Units: Metric or US units. Weight and height are converted in place when you switch.

BMR formula

Mifflin-St Jeor: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (men) or − 161 (women) · Harris-Benedict (revised 1984): men 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age; women 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age

\text{BMR} = 10W + 6.25H - 5A + s, \quad s = +5 \text{ (men)},\ -161 \text{ (women)}

Basal metabolic rate is the energy your body uses at complete rest — breathing, circulation, keeping warm, running the organs — before any activity. It cannot be measured at home, so equations estimate it from weight, height, age and sex. Mifflin-St Jeor (1990) was fitted to 498 healthy adults and is the one dietitians usually recommend; the Harris-Benedict equation dates from 1919 and is used here in its 1984 revision, which tends to run a little higher. Weight and height go in as kilograms and centimetres (imperial entries are converted), and the answer is calories a day. BMR is the floor: multiply it by an activity factor to get total daily energy — the maintenance-calories calculator does that step.

BMR worked example

A 30-year-old man, 70 kg and 175 cm, by Mifflin-St Jeor: 10 × 70 = 700, plus 6.25 × 175 = 1,093.75, minus 5 × 30 = 150, plus 5, gives 1,648.75 — about 1,649 kcal a day, or 69 an hour. The revised Harris-Benedict equation gives 1,696 for the same man, 47 higher. A woman of the same size and age would be 1,483 by Mifflin-St Jeor, because the constant is −161 instead of +5.

More BMR examples

A 45-year-old woman, 165 cm and 60 kg, by Mifflin-St Jeor: 10 × 60 + 6.25 × 165 − 5 × 45 − 161 = 1245 kcal/day at rest. The revised Harris-Benedict equation puts her at 1,319, a reminder that both are estimates.

Where the BMR calculator can give the wrong answer

Both equations are averages for healthy adults with a typical amount of muscle. Very muscular people burn more at rest than the estimate and very lean or very overweight people less closely fit; the error for an individual is commonly ±10%.
They were fitted to adults. For children, teenagers, pregnancy or people over about 70, the coefficients do not apply and the number should not drive a diet.
BMR is not the calories you should eat. It is what you would burn lying still all day; daily needs are BMR times an activity factor, usually 1.2–1.9, and a deficit is taken from that total.
Mifflin-St Jeor and Harris-Benedict disagree by 50–150 kcal for most adults. That gap is smaller than the day-to-day noise in what people eat, so pick one and stick with it.
Thyroid conditions, fever, some medicines and recent rapid weight loss all shift real resting metabolism away from any equation.

Spotted a mistake? Tell us

BMR FAQ

: 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. A 60 kg, 165 cm woman of 40: 600 + 1,031 − 200 − 161 = 1,270 kcal a day. Enter your figures above and the working is shown.
: BMR is the energy used at complete rest. TDEE — total daily energy expenditure, also called maintenance calories — adds everything else: moving, working, exercising, digesting. TDEE is BMR times an activity factor from about 1.2 (desk-bound) to 1.9 (hard daily training). The maintenance-calories calculator applies those factors.
: Mifflin-St Jeor, in most comparisons on modern adults, which is why the Academy of Nutrition and Dietetics and most calculators use it. Harris-Benedict, even revised, was fitted to a leaner early-20th-century sample and tends to overestimate slightly. Both are shown here so you can see the gap.
: On average women carry a higher share of body fat and less muscle at the same weight and height, and fat tissue uses less energy at rest than muscle. The −161 constant in the women's equation is how the fitted data expressed that difference; it is an average, not a rule for any one person.
: Nearly. BMR is measured fasted and at complete rest just after waking; resting metabolic rate is measured under looser conditions and runs a little higher. Mifflin and St Jeor fitted their equation to resting energy expenditure, so it estimates the latter.