BMR Calculator
Calculate basal metabolic rate via Mifflin-St Jeor, Harris-Benedict or Katch-McArdle.
About BMR Calculator
Your Basal Metabolic Rate is the number of calories your body needs to maintain basic functions at complete rest. It's calculated with the Mifflin-St Jeor equation, the current clinical standard.
Formulas
Mifflin-St Jeor — Male
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
- BMR
- Basal Metabolic Rate in kcal/day
- w
- Weight in kilograms
- h
- Height in centimetres
- a
- Age in years
Mifflin-St Jeor — Female
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
- BMR
- Basal Metabolic Rate in kcal/day
- w
- Weight in kilograms
- h
- Height in centimetres
- a
- Age in years
Worked example
With the default values below, BMR Calculator returns BMR (calories/day at rest) of 1,649. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Unitsone of Metric (kg, cm), Imperial (lb, in)
- Metric (kg, cm)
- Sexone of Male, Female
- Male
- Weightaccepts 1–700 kg / lb
- 70 kg / lb
- Heightaccepts 30–260 cm / in
- 175 cm / in
- Ageaccepts 1–120 years
- 30 years
Results
- BMR (calories/day at rest)
- 1,649
Step by step
- 1Weight term: 10 × kg= 700.00 kcal
- 2Height term: 6.25 × cm= 1,093.75 kcal
- 3Age term: 5 × age= 150.00 kcal
- 4Apply sex constant (+ 5)= 1,649 kcal/dayMale offset is +5 (Mifflin-St Jeor)
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- This is an estimate and not medical advice. BMR varies with body composition and health status. Consult a healthcare professional before making dietary changes.
- This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
BMR Calculator — full guide
The floor under every other calorie number
Basal Metabolic Rate is what your body spends while you lie still: circulation, breathing, kidney and liver work, brain activity, tissue repair. Nothing you do voluntarily is in it. It matters because every daily-calorie figure is built on top of it — at the moderate activity factor of 1.55, BMR is about 65% of total daily expenditure (1 ÷ 1.55).
The equation
This page uses Mifflin-St Jeor. The two forms are identical except for the last term:
- Men:
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 - Women:
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Weight is in kilograms, height in centimetres, age in whole years. Nothing else enters the calculation.
Worked example
A woman of 62 kg, 165 cm, aged 34:
| Term | Arithmetic | Value |
|---|---|---|
| Weight | 10 × 62 | 620 |
| Height | 6.25 × 165 | 1,031.25 |
| Age | −5 × 34 | −170 |
| Sex constant | female | −161 |
| BMR | sum of the rows | 1,320 kcal/day |
The 166-calorie gap
Run one body through both forms. At 70 kg, 175 cm and 30 years the male version returns 1,648.75 kcal and the female version 1,482.75 kcal — a fixed 166 kcal apart, since +5 and −161 are constants. The gap never changes with size; it is the equation's allowance for average differences in lean mass.
Working in pounds and inches
Switch the units selector and the inputs are converted before the formula runs, using 1 lb = 0.453592 kg and 1 in = 2.54 cm exactly. So 154 lb becomes 69.85 kg, 65 in becomes 165.1 cm, and a 40-year-old man with those measurements gets 1,535 kcal/day.
Assumptions worth knowing
- It is not an eating target. Multiply by an activity factor first — the calorie calculator and TDEE calculator do that step.
- Total weight is the only body input, so composition is invisible to it. Muscle is more metabolically active at rest than fat, so a lean, heavily trained person usually sits above the estimate and someone carrying more fat at the same weight sits below. The body fat calculator gives you that missing dimension.
- The age term is linear: 10 years costs exactly 50 kcal in this model, which understates what actually changes with age, since activity and muscle mass tend to fall too.
- This is an estimate rather than medical advice; thyroid conditions, medication and illness can move true resting expenditure well outside it.
This is an estimate and not medical advice. BMR varies with body composition and health status. Consult a healthcare professional before making dietary changes.
Frequently Asked Questions
How do I use my BMR?
Multiply it by an activity factor to estimate your total daily calorie needs (TDEE). Use our Calorie Needs calculator for that step.
Why Mifflin-St Jeor?
It's more accurate for modern populations than the older Harris-Benedict equation and is widely used by dietitians.
Does the age term mean my metabolism really drops 5 calories a year?
That is what the equation says — 10 years at the same height and weight removes exactly 50 kcal — but it is a statistical slope fitted across people, not a measurement of you. Real declines usually come from losing muscle and moving less, which the formula cannot see because it only knows total weight.
Two of us weigh 70 kg and stand 175 cm but get different BMRs — why?
Only three inputs can differ: age, which costs 5 kcal per year, and sex, which is a flat 166 kcal gap between the +5 and −161 constants. At 70 kg, 175 cm and 30 years the male result is 1,649 kcal and the female result 1,483 kcal. Identical inputs always give identical output.
Is eating exactly my BMR a reasonable diet plan?
It is a steeper cut than it looks. The 1,320 kcal example woman burns roughly 2,046 kcal a day at the moderate 1.55 factor, so eating her BMR is a 726 kcal deficit — well past the 500 kcal that equals about a pound a week. Aim for a moderate gap and discuss sustained low intakes with a clinician.
Should I use lean body mass instead of total weight?
Mifflin-St Jeor is defined on total weight, so this page cannot take lean mass. Equations built on lean mass, such as Katch-McArdle, need a reliable body-composition measurement to be worth the swap. If you only have a tape measure, the circumference-based estimate from the body fat page is the realistic input.