How to calculate your BMR
- Choose Metric or US units and your Sex.
- Enter your Age, height and weight. Add your Body fat % if you know it to see the Katch-McArdle figure too.
- Read your BMR from the Mifflin-St Jeor equation, the other formulas below it and the calories you need a day at each activity level.
The three equations
Weight is in kilograms, height in centimetres and age in years. US units are converted first.
| Equation | Women | Men |
|---|---|---|
| Mifflin-St Jeor (1990) | 10 × weight + 6.25 × height − 5 × age − 161 | 10 × weight + 6.25 × height − 5 × age + 5 |
| Harris-Benedict, revised by Roza and Shizgal (1984) | 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age | 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age |
| Katch-McArdle | 370 + 21.6 × lean body mass | same as women |
For the default example, a 35-year-old woman who is 168 cm tall and weighs 68 kg, Mifflin-St Jeor gives 680 + 1,050 − 175 − 161 = 1,394 calories a day. Harris-Benedict gives about 1,445. At 25% body fat her lean mass is 51 kg, so Katch-McArdle gives 370 + 21.6 × 51 = 1,472.
What changes your BMR
Bigger bodies burn more at rest, so BMR rises with weight and height. It falls slowly with age, partly because people tend to lose muscle as they get older, and men usually have a higher BMR than women of the same size because they carry more muscle on average. That is why Katch-McArdle, which ignores sex and age and looks only at lean mass, can give a different answer from the other two.
From BMR to daily calories
Your BMR is not what you should eat. The table under the result multiplies it by the standard activity factors, from 1.2 for little or no exercise to 1.9 for very hard training or a physical job. That total is your TDEE, the calories that keep your weight steady.