WiseCalcs

BMR calculator

Enter your weight, height, age, and sex. The calculator estimates your basal metabolic rate with the Mifflin-St Jeor equation and shows the energy in kilojoules and per hour.

Use it to see how many calories your body burns at complete rest, before any activity.

kg
cm

BMR

1,780 kcal

Energy (kJ)
7,448 kJ
Per hour
74.2 kcal

The result updates as you type. The headline is your BMR in kcal per day; the others give the kilojoule equivalent and an hourly figure. This BMR is an estimate only. It does not replace medical or nutritional advice — individual metabolism varies and a professional can interpret your needs.

How does it work?

BMR is the energy your body uses at complete rest. Multiply it by an activity factor to get total daily energy (TDEE). The Mifflin-St Jeor equation is the most widely recommended estimate.

Mifflin-St Jeor BMR formula

BMR=10w+6.25h−5a+s\text{BMR} = 10w + 6.25h - 5a + s
BMR
Basal metabolic rate in kcal/day.
w
Weight in kilograms.
h
Height in centimetres.
a
Age in years.
s
Sex constant: +5 male, −161 female.

An 80 kg, 180 cm, 30-year-old man: 10×80 + 6.25×180 − 5×30 + 5 = 1780 kcal/day at rest.

Expert tips

  • This BMR is an estimate only. It does not replace medical or nutritional advice — individual metabolism varies and a professional can interpret your needs.

Method & sources

We estimate resting energy with the Mifflin-St Jeor equation from your weight, height, age, and sex. The linked research paper below is the primary reference for that formula. You enter the measurements yourself — the calculator does not access medical records.

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

How we calculate

  • The Mifflin-St Jeor equation is used.
  • Weight is in kilograms, height in centimetres, age in years.
  • BMR is resting energy only; it excludes activity.
  • The sex constant is +5 for males and −161 for females.

Limitations

  • This BMR is an estimate only. It does not replace medical or nutritional advice — individual metabolism varies and a professional can interpret your needs.

Rounding

BMR is shown as whole kcal; the per-hour figure to one decimal. The calculation uses full precision.

What this calculator does

Basal metabolic rate is the energy your body needs to keep functioning at complete rest. This calculator uses the Mifflin-St Jeor equation — the most widely recommended estimate — to work it out from your weight, height, age, and sex.

How to use it

  1. Enter your weight in kilograms.
  2. Enter your height in centimetres.
  3. Enter your age and pick your sex.
  4. Read your BMR in kcal per day.

A worked example

An 80 kg, 180 cm, 30-year-old man: 10×80 + 6.25×180 − 5×30 + 5 = 1780 kcal per day at rest, about 7447 kJ or roughly 74 kcal per hour.

From BMR to daily calories

BMR covers rest only. To estimate the calories you actually burn in a day, multiply BMR by an activity factor — that gives your TDEE, which is what you'd use to plan eating for a goal.

Common mistakes

  • Entering weight in pounds or height in inches.
  • Treating BMR as your full daily calorie need — it excludes activity.
  • Expecting precision: it's an estimate, individuals vary.

When it's useful

As the foundation for a calorie plan, a baseline for tracking, or to understand how much energy your body uses just to stay alive.

FAQ

What is BMR?
Basal metabolic rate is the energy your body uses at complete rest to run basic functions like breathing and circulation.
Which equation does it use?
The Mifflin-St Jeor equation, which is generally the most accurate of the common BMR formulas for the wider population.
What's the difference between BMR and TDEE?
BMR is resting energy. TDEE adds activity by multiplying BMR by an activity factor, giving your total daily energy expenditure.
Why does sex change the result?
The equation adds 5 for males and subtracts 161 for females, reflecting average differences in body composition.
How accurate is it?
It's a solid estimate for most people, but individual metabolism varies. Use it as a starting point, not an exact figure.
Can I share a calculation?
Yes. Use Share to copy a link that reopens the calculator with the same details.

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