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BMR Calculator

With weight 75 kg, height 175 cm, age 30 years, body fat, if you know it 0 percent, bmr comes to 1,699 kcal/day — bmr, mifflin-st jeor. It is reached in 8 steps, the last of which is 10 * weight + 6.25 * height - 5 * age + (sex_male ? 5 : -161), and each one is printed on the page with its numbers filled in. The formula is the one published by Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7., not an approximation fitted to it.

Basal metabolic rate from the Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle equations at once, with the disagreement between them shown.

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Weight 75 kg, Height 175 cm, Age 30 years, Sex Male

1,699 kcal/day

BMR, Mifflin-St Jeor for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.

It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.

BMR, Mifflin-St Jeor
1,699 kcal/day
Mifflin-St Jeor
10 * weight + 6.25 * height - 5 * age + (sex_male ? 5 : -161)1,698.75 kcal/day
Harris-Benedict, revised
1,762.652 kcal/day
Lean body mass
body_fat == 0 ? 0 : weight * (1 - body_fat / 100)0 kg
Katch-McArdle
body_fat == 0 ? 0 : 370 + 21.6 * lean_mass0 kcal/day
Lowest estimate
1,698.75 kcal/day
Highest estimate
1,762.652 kcal/day
How far apart they are
lowest == 0 ? 0 : (highest - lowest) / lowest * 1003.762 %
Calories an hour at rest
mifflin / 2470.781 kcal/hr

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Worked example

A 30-year-old man of 75 kg and 175 cm: Mifflin-St Jeor gives 1,699 kcal a day and the revised Harris-Benedict gives 1,763. The 64 calories between them are not a rounding difference — they are two equations fitted to two different samples, and the published error on either is larger than the gap.

How to work it out yourself

  1. 1.Enter height, weight, age and sex. Every equation here needs those four and nothing else.
  2. 2.Add body fat only if it was measured rather than guessed. A caliper or a smart scale reading is worth using; an estimate from a photograph makes the Katch-McArdle figure less reliable than the equations that ignore it.
  3. 3.Read the spread. That is the honest width of the answer, before any activity multiplier widens it further.

The formula

  1. Mifflin-St Jeor10 * weight + 6.25 * height - 5 * age + (sex_male ? 5 : -161)
  2. Harris-Benedict, revised
  3. Lean body massbody_fat == 0 ? 0 : weight * (1 - body_fat / 100)
  4. Katch-McArdlebody_fat == 0 ? 0 : 370 + 21.6 * lean_mass
  5. Lowest estimate
  6. Highest estimate
  7. How far apart they arelowest == 0 ? 0 : (highest - lowest) / lowest * 100
  8. Calories an hour at restmifflin / 24

Source: Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7., Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr. 1984;40(1):168–82., Cunningham JJ. A reanalysis of the factors influencing basal metabolic rate in normal adults. Am J Clin Nutr. 1980;33(11):2372–4.

Questions people actually ask

Which equation should I use?
Mifflin-St Jeor for most people — it was fitted on a more recent population than Harris-Benedict and validates better against measured expenditure, which is why the Academy of Nutrition and Dietetics recommends it. Use Katch-McArdle instead when you have a real body composition measurement, since it is the only one that distinguishes two people of the same height and weight.
Why do the three answers differ?
Because they are regressions on different samples. Harris and Benedict measured 239 people around 1918 and the sample was leaner than a modern one; Mifflin and St Jeor measured 498 people in the late 1980s; Cunningham reanalysed data on lean mass. Each fits its own data and none of them measured you. The typical published error is around 10% either way, which is wider than the gap between the equations.
What is the difference between BMR and RMR?
BMR is measured after an overnight fast, at rest, at a comfortable temperature, having not moved since waking — conditions that essentially require a laboratory. RMR relaxes those conditions and runs about 10% higher. Every equation on this page is fitted to measured resting expenditure, so what they predict is closer to RMR than to a true basal figure, whatever they are called.
Is BMR the same as calories burned in a day?
No — it is what you would burn doing nothing at all, and it is usually 60 to 70% of the daily total. Digestion adds around 10% and movement adds the rest. The TDEE calculator applies an activity multiplier to this figure to get the number that matters for eating.
Does a lower BMR mean a slow metabolism?
Usually it means a smaller body. BMR scales with lean mass above everything else, so a shorter or lighter person burns less at rest by arithmetic rather than by any metabolic defect. Genuine differences between people of the same size and composition are real but modest — the "myth of feminine metabolism" paper is titled that for a reason.

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