CALCULATOR 02

BMR Calculator

The calories your body burns at complete rest, estimated with three well-known formulas.

Your BMR

Choose the sex used in the formulas.

For general information only; not medical advice. Consult a qualified professional before making health decisions.

How this is calculated

Mifflin-St Jeor (1990) — default

Men:   10 × weight + 6.25 × height − 5 × age + 5
Women: 10 × weight + 6.25 × height − 5 × age − 161

Revised Harris-Benedict (Roza & Shizgal, 1984)

Men:   88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
Women: 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age

Katch-McArdle (needs body fat %)

Lean body mass = weight × (1 − body fat % ÷ 100)
BMR = 370 + 21.6 × lean body mass

Weight in kg, height in cm, age in years.

Sources

Mifflin MD et al. (1990), A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51:241–247.
Roza AM, Shizgal HM (1984), The Harris Benedict equation reevaluated. Am J Clin Nutr 40:168–182.
Katch-McArdle — McArdle WD, Katch FI, Katch VL, Exercise Physiology: Nutrition, Energy, and Human Performance.

What BMR is

Basal metabolic rate is the energy your body uses to stay alive at complete rest: breathing, pumping blood, repairing cells and keeping you warm. For people who aren't very active it's usually the largest part of the calories they burn in a day, often around 60–70%.

Which formula to use

Mifflin-St Jeor is the default because, in comparison studies, it has predicted measured resting energy most reliably for healthy adults. The revised Harris-Benedict equation is older and tends to give slightly higher numbers. Katch-McArdle works differently: it ignores age and sex and uses lean body mass instead, so it can suit people who know their body fat percentage and are leaner or more muscular than average.

The comparison in your results shows every formula you have data for, so you can see how much they agree.

Why estimates differ from reality

All three are prediction equations built from groups of people. Your actual BMR can be 10% or more above or below the estimate because of genetics, muscle mass, hormones, medication or illness. Treat the number as a starting point, then adjust your intake based on how your weight actually changes over two to four weeks.

BMR, RMR and TDEE

Strictly, BMR is measured fasted, fully rested and in a warm room; resting metabolic rate (RMR) uses looser conditions and runs slightly higher. In practice the equations are used for both. Neither includes movement or exercise—for that, multiply by an activity factor in the TDEE calculator.

Frequently asked questions

What's the difference between BMR and TDEE?

BMR is the energy you burn at complete rest. TDEE (total daily energy expenditure) adds everything else—digestion, daily movement and exercise—so it's always higher. Use TDEE, not BMR, to plan how much to eat.

Which BMR formula is most accurate?

For most healthy adults, Mifflin-St Jeor has performed best in comparison studies. If you know your body fat percentage and you're leaner or more muscular than average, Katch-McArdle may suit you better.

Why does Katch-McArdle need my body fat percentage?

It estimates BMR from lean body mass—your weight minus fat—because muscle and organs drive most resting energy use. Without body fat %, lean mass can't be calculated. You can estimate it with the Body Fat calculator.

Should I eat less than my BMR to lose weight?

Generally no. Eating below BMR for long periods makes it hard to get enough nutrients and protect muscle. Most people lose weight well eating between their BMR and their TDEE.