BMR Calculator

Choose male or female, then enter age in years, height in centimetres and weight in kilograms. The tool applies the Mifflin-St Jeor equation (1990) and shows the answer in kcal per day, rounded to a whole number:

• Men: 10W + 6.25H − 5A + 5
• Women: 10W + 6.25H − 5A − 161

W is weight in kg, H is height in cm and A is age. The defaults (male, 30, 175 cm, 70 kg) give 1,649 kcal/day. The same inputs set to female give 1,483. The paper that published the equation calls it resting energy expenditure, and like any prediction equation it gives an estimate, not a measurement or a diagnosis.

A 30-year-old woman who is 165 cm tall and weighs 62 kg:

1. 10 × 62 = 620
2. 6.25 × 165 = 1,031.25
3. 5 × 30 = 150, which is subtracted
4. 620 + 1,031.25 − 150 − 161 = 1,340.25

The tool shows 1,340 kcal/day. Doing it once by hand like this is a good way to check you typed the inputs in the right boxes, since swapping height and weight gives a very different number.

Because the equation is a straight sum, every input has a fixed effect:

So a 20-year age gap changes the estimate by 100 kcal, the same as 10 kg of body weight. Nothing else is taken into account: there is no box for body fat, muscle or health conditions.

Some tools use the revised Harris-Benedict equation (Roza and Shizgal, 1984) instead. As it is usually published, the male version is 88.362 + 13.397W + 4.799H − 5.677A. For the default man it gives about 1,696 kcal, roughly 47 more than this tool. Neither result is wrong; they are different prediction equations. If you are comparing figures from two places, check which equation each one uses before reading anything into the gap.