MultiConvers

BMR Calculator

Estimate basal metabolic rate with Mifflin-St Jeor (1990) from sex, age, height and weight. The number is kcal per day at complete rest — not what you burn walking around, and not Harris-Benedict.

Updated

How to use

  1. Choose metric or US units, then enter the sex the equation should use (the paper’s two intercepts).
  2. Enter age in years (this page accepts 1–120), weight, and height in centimetres or feet and inches.
  3. Read BMR as a whole number of kcal/day. An 80 kg, 180 cm, 30-year-old using the male equation is 1780.
  4. Open the Calorie Calculator if you want that BMR multiplied by a 1.2–1.9 activity factor (TDEE). This page stops at rest.

How it works

Mifflin, St Jeor and colleagues published a resting-energy equation that uses kilograms, centimetres and age: 10×kg + 6.25×cm − 5×age, then +5 or −161. Those two constants are how the 1990 paper coded the two groups in their sample. They are not a verdict about hormones, muscle or identity, and this page will not invent a third intercept.

Worked numbers stay ordinary. Male equation, 80 kg, 180 cm, age 30: 10×80 + 6.25×180 − 5×30 + 5 = 800 + 1125 − 150 + 5 = 1780 kcal/day. That is energy at rest, closer to a lab reclining measurement than to a day of commuting and fidgeting. It is not TDEE and it is not the calories of one gym session.

Harris-Benedict (1919, revised 1984) is the older pair of equations you still see on some charts. This site does not run those formulas. Mifflin-St Jeor is the equation used here because it is the one most often recommended for contemporary adults in dietetic teaching materials. “Most often recommended” is not the same as “measured on you.”

Age, height and weight are converted from US units when you ask for them. Age outside 1–120, or a result that would not be a positive finite number, is rejected. The output is rounded to a whole kilocalorie because the inputs are not precise enough to justify tenths.

For a maintenance estimate that includes movement, use the Calorie Calculator (BMR × 1.2 sedentary through 1.9 very active). For one activity, use Calories Burned (MET × kg × hours). Neither is a prescription. Not medical advice.

Formula

Male: 10×kg + 6.25×cm − 5×age + 5
Female: 10×kg + 6.25×cm − 5×age − 161

Worked examples

  • Worked Mifflin-St Jeor example

    male equation, 80 kg, 180 cm, age 30 → 1780 kcal/day

Useful notes

  • Mifflin-St Jeor (1990) only — Harris-Benedict is not used on this page.
  • Result is resting kcal/day, not total daily energy expenditure.
  • Not medical advice.

FAQ

What is BMR?

An estimate of energy used at complete rest. It is not the calories you burn in a day of normal life.

Why Mifflin-St Jeor?

It is a widely cited update to older resting-energy equations and uses simple kg/cm/age inputs.

Is this a prescription?

No. It is an equation output, not a diet plan.

Does this include exercise?

No. BMR is rest only. Multiply by an activity factor on the Calorie Calculator, or cost one session on Calories Burned.

What ages does the equation accept?

This page rejects age at or below 0 and above 120. The original paper was fitted on adults; a number for a child is still just the algebra.

Related tools

See all Fitness tools.

Sources