BMR calculator

The energy your body uses at rest, for breathing, pumping blood and keeping you at 37°C. Mifflin-St Jeor, Harris-Benedict, the Henry equations behind UK energy values and, with a body fat figure, Katch-McArdle, side by side.

Your details

Your resting energy (BMR)

1,370

kcal a day at complete rest

Mifflin-St Jeor1,369 kcal
Harris-Benedict (revised)1,432 kcal
Henry (Oxford), used by SACN for UK energy values, age 30 to 591,373 kcal
Spread between the equations62 kcal; add a body fat % for a lean mass estimate
Per hour, roughly57 kcal

This is the energy your body uses lying still: breathing, keeping warm, thinking. The equations are averages from groups, so for one person each can be 10% or so out, which is why we show them side by side. Everyday life adds 20% to 90% on top, so this is a floor, not a target.

The working

Mifflin-St Jeor, step by step

Most UK dietitians and apps use the 1990 Mifflin-St Jeor equation. It uses kilograms, centimetres and years:

Women: 10 × kg + 6.25 × cm − 5 × age − 161
Men: 10 × kg + 6.25 × cm − 5 × age + 5

A 40 year old woman at 5 ft 5 in (165.1 cm) and 11 st (69.9 kg): 698.5 + 1,031.9 − 200 − 161 = 1,369 kcal, which we round to 1,370.

The UK equation

Henry, as used by SACN

The Scientific Advisory Committee on Nutrition based the UK energy reference values (2011) on Henry's Oxford equations, which use only weight and an age band. For a woman of 30 to 59: (0.0407 × 69.9 + 2.90) MJ = 5.74 MJ, or 1,373 kcal, within a few kcal of Mifflin here. Add a body fat percentage and Katch-McArdle works from lean mass instead: at 32%, 47.5 kg lean gives 370 + 21.6 × 47.5 = 1,396 kcal.

Second opinion

Why show Harris-Benedict too?

The Harris-Benedict equation dates from 1918 and was refitted by Roza and Shizgal in 1984. It tends to come out a little higher, around 60 kcal here. Seeing both reminds you that BMR is an estimate: measured values for people of the same size can differ by 10% either way.

Using it

BMR is a floor, not a goal

Nobody lives at their BMR. Getting dressed, walking to the bus and fidgeting all add up, which is why your everyday number (TDEE) is usually 20% to 90% higher. Our deficit tools never suggest eating below your BMR, and NHS advice is that very low calorie diets need medical supervision.

Read with care

What this cannot tell you

MuscleTwo people of the same weight with more or less muscle burn different amounts.
Thyroid and medicinesAn under or overactive thyroid, and some medicines, change it a lot.
Under 18sGrowing bodies need more, so this is for adults only.

Questions

Common questions

What is a normal BMR?

For most adults it falls between about 1,200 and 2,000 kcal a day. Taller, heavier and more muscular people sit higher, and it drifts down slowly with age.

Is BMR the same as RMR?

Nearly. BMR is measured in strict lab conditions after a night's sleep and fasting; resting metabolic rate (RMR) is a little more relaxed and usually slightly higher. The formulas here estimate either.

Can I raise my BMR?

A little, by building muscle with strength training. Most "metabolism boosting" foods and supplements make no meaningful difference.

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

If food feels hard

If eating, weight or food is on your mind a lot, you are not alone. Your GP can help, and Beat has a free helpline on 0808 801 0677 (England, weekdays 3pm to 8pm).