Skip to content

BMR Calculator

Calculate the calories your body burns at complete rest using the Mifflin-St Jeor, Harris-Benedict or Katch-McArdle equation.

Formulas last reviewed: September 2026

Disclaimer: Results are general estimates for information and education only. They are not medical advice, a diagnosis or a treatment plan. Please talk to a doctor or qualified health professional before making health, diet, exercise or pregnancy decisions.

What is BMR?

Basal metabolic rate (BMR) is the number of calories your body burns at complete rest — breathing, circulating blood and keeping organs working. It usually makes up 60–70% of the calories you burn in a day.

Knowing your BMR is the first step to working out how much to eat, and it is why weight-loss plans should never go far below it.

How it is calculated

Mifflin-St Jeor: 10 × kg + 6.25 × cm − 5 × age + 5 (men) / − 161 (women)
Harris-Benedict (revised), Katch-McArdle: 370 + 21.6 × lean mass (kg)

Mifflin-St Jeor is the most widely recommended. Katch-McArdle uses lean body mass, so it suits muscular people if you know your body fat percentage.

Worked example

Man, 30 years, 170 cm, 70 kg

Mifflin-St Jeor
1,618 kcal
Harris-Benedict
1,672 kcal
Katch-McArdle (20% fat)
1,580 kcal
Moderately active (× 1.55)
2,507 kcal/day

What changes your BMR?

  • Muscle mass — more muscle raises BMR.
  • Age — BMR falls slowly after about 30.
  • Sex — men usually have higher BMR because of more muscle.
  • Body size, thyroid function and illness also matter.

BMR is not the number of calories to eat. Multiply it by an activity factor to get your daily needs, or use the TDEE calculator.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is calories burned at rest. TDEE (total daily energy expenditure) adds movement and exercise, so it is always higher.

Which BMR formula is most accurate?

Mifflin-St Jeor is generally the best for most adults. Katch-McArdle can be better for very lean or muscular people who know their body fat.

Can I raise my BMR?

Building muscle with strength training and eating enough protein helps. Extreme dieting can lower BMR over time.

Should I eat below my BMR to lose weight?

It is not recommended. Eating far below BMR can cost muscle and energy. Aim for a moderate gap below your TDEE instead.