BMR Calculator

Find your basal metabolic rate – the calories your body uses at complete rest – and compare three formulas.

Result

Basal metabolic rate (BMR)

    Daily calories by activity level

    years
    cm
    kg
    %

    How to use the BMR calculator

    1. Choose units and enter your sex, age, height and weight.
    2. If you know your body fat percentage, enter it to add the Katch-McArdle formula. If not, use the body fat calculator first, or leave it empty.
    3. Press Calculate for your BMR, a comparison of the formulas, and your daily calories at each activity level.

    What is BMR?

    Basal metabolic rate is the energy your body needs to stay alive at complete rest – breathing, pumping blood, keeping warm, running the brain and organs. It is measured lying still, after a night's sleep and 12 hours without food, so the figure leaves out all movement and digestion. For most people it is 60–70% of the calories they burn in a day.

    RMR (resting metabolic rate) is measured under looser conditions and is usually a few percent higher. The two names are often used for the same thing, and the formulas here estimate either.

    The three formulas

    FormulaUsesBest for
    Mifflin-St Jeor (1990)weight, height, age, sexmost adults – the most accurate of the common equations in comparison studies
    Revised Harris-Benedict (1984)weight, height, age, sexa widely known alternative; tends to give a slightly higher figure
    Katch-McArdleweight and body fat %lean or muscular people who know their body fat

    With weight W in kg, height H in cm, age A in years and body fat F in %:

    Mifflin-St Jeor

    \begin{aligned} \text{Men: } & 10W + 6.25H - 5A + 5 \\ \text{Women: } & 10W + 6.25H - 5A - 161 \end{aligned}

    Revised Harris-Benedict

    \begin{aligned} \text{Men: } & 13.397W + 4.799H \\ & - 5.677A + 88.362 \\ \text{Women: } & 9.247W + 3.098H \\ & - 4.330A + 447.593 \end{aligned}

    Katch-McArdle

    370 + 21.6\,W(1 - F/100)
    Example: a 40-year-old man, 180 cm, 80 kg, 20% body fat
    • Mifflin-St Jeor: 10(80) + 6.25(180) - 5(40) + 5 = 1{,}730 kcal
    • Revised Harris-Benedict: 13.397(80) + 4.799(180) - 5.677(40) + 88.362 = 1{,}797 kcal
    • Katch-McArdle: lean mass 80 \times 0.8 = 64 kg, so 370 + 21.6 \times 64 = 1{,}752 kcal

    The formulas agree to within 67 kcal, a normal spread.

    Average BMR by age

    Mifflin-St Jeor BMR for a man of 178 cm and 80 kg, and a woman of 165 cm and 65 kg:

    AgeMan (kcal/day)Woman (kcal/day)
    201,8181,420
    301,7681,370
    401,7181,320
    501,6681,270
    601,6181,220
    701,5681,170
    801,5181,120

    BMR falls by about 50 kcal a day for every 10 years of age in these formulas, mostly because muscle mass tends to fall.

    What changes your BMR

    • Body size: a heavier, taller body has more tissue to run.
    • Muscle: lean tissue uses more energy than fat, which is why the Katch-McArdle formula uses lean mass only.
    • Age and sex: BMR slowly falls with age; men usually have more muscle and a higher BMR at the same weight.
    • Other factors: genetics, thyroid hormones, illness, fever and some medicines. Crash dieting can lower it for a while.

    Strength training that builds muscle is the most reliable way to raise BMR, though the effect is modest – roughly 13 kcal a day per extra kilogram of muscle.

    From BMR to daily calories

    To find how much to eat, multiply your BMR by an activity factor from 1.2 (sedentary) to 1.9 (very hard daily exercise). The result shows each level, and the TDEE calculator explains how to choose yours.

    BMR formulas are estimates for healthy adults. A dietitian or clinic can measure your resting metabolic rate directly with indirect calorimetry if you need an exact figure.

    Frequently asked questions

    What is a normal BMR?

    For most adults, roughly 1,200–1,600 kcal a day for women and 1,500–2,000 kcal for men. It depends on your size, age, sex and muscle mass.

    Which BMR formula is the most accurate?

    Mifflin-St Jeor is the most accurate of the common equations for most adults. If you know your body fat percentage, Katch-McArdle can be closer for lean or muscular people.

    Should I eat my BMR to lose weight?

    Not as a rule. Your BMR is what you need at total rest, so eating only that much is a large deficit for most people. Base a weight-loss target on your TDEE instead.

    Is BMR the same as calories burned per day?

    No. BMR is only the resting part. Calories burned per day (TDEE) add digestion, exercise and everyday movement, usually 1.2 to 1.9 times your BMR.

    Does BMR go down as you lose weight?

    Yes. A smaller body needs less energy, so your BMR falls as you lose weight. Recalculate after every few kilograms lost.