BMR
calculator.

How do you calculate BMR?

Put your weight in kilograms, height in centimetres and age in years into a prediction equation. With Mifflin-St Jeor, a 35-year-old man who is 5 ft 10 in (177.8 cm) and 180 lb (81.65 kg) has BMR = 10 × 81.65 + 6.25 × 177.8 − 5 × 35 + 5 = 816.47 + 1,111.25 − 175 + 5 = 1,758 kcal a day. That is the energy his body would use lying at rest, before any activity or digestion.

Men:   BMR = 10W + 6.25H − 5A + 5
Women: BMR = 10W + 6.25H − 5A − 161
W = kg, H = cm, A = years

Which BMR formula is the most accurate?

No equation is right for everyone, so this calculator shows all three. Mifflin and colleagues built their equation from 498 healthy adults measured by indirect calorimetry and found that the 1919 Harris-Benedict equations overestimated measured resting energy by 5%. A 2021 study of healthy women found that the best equation depended on age and weight, and even the best one placed fewer than half of the women within ±10% of their measured value. For the same 35-year-old man, revised Harris-Benedict gives 1,837 kcal against Mifflin’s 1,758, a gap of 79 kcal (4.5%).

How do you calculate BMR with body fat percentage?

Katch-McArdle uses lean body mass instead of total weight: BMR = 370 + 21.6 × lean mass in kg. A 50-year-old man of 95 kg with 22% body fat has 95 × 0.78 = 74.1 kg of lean mass, so BMR = 370 + 21.6 × 74.1 = 1,971 kcal. Mifflin-St Jeor gives 1,849 kcal and revised Harris-Benedict 1,955 kcal for him. The lean-mass equation is only as good as the body fat figure, so use a measured value if you have one.

BMR = 370 + 21.6 × LBM
LBM = weight (kg) × (1 − body fat % ÷ 100)

What is the difference between BMR and RMR?

Strictly, basal metabolic rate is measured fasted, at complete rest, just after waking, and resting metabolic rate (or resting energy expenditure) is measured at rest under looser conditions. The Mifflin-St Jeor paper predicts resting energy expenditure, and most calculators, including this one, use the name BMR for it. The difference matters for laboratory work but is small next to the error of any prediction equation.

How do I get from BMR to the calories I need each day?

Multiply BMR by a physical activity level (PAL): total daily energy ÷ BMR. FAO/WHO/UNU’s worked examples use 1.53 for a sedentary or light lifestyle and 1.76 for a moderately active one, so a BMR of 1,758 kcal becomes about 2,690 or 3,094 kcal a day. The calorie calculator does this, and also offers the NASEM 2023 equations, which predict daily needs directly from measured energy use.