BMR Calculator
Find out how many calories your body burns at rest. Compare three proven formulas and see your daily calorie needs at five activity levels.
Daily calories by activity level
| Activity level | Mifflin-St Jeor | Harris-Benedict | Katch-McArdle |
|---|
Daily calories (TDEE) = BMR × activity multiplier. These are estimates; real needs can differ by 10% or more.
How to use the BMR Calculator
- Choose metric or imperial and select your sex.
- Enter your age, height and weight. Add your body fat percentage if you know it to unlock the Katch-McArdle formula.
- Press Calculate to compare your BMR from each formula.
- Check the activity table to see how many calories you burn per day at each activity level.
BMR formulas
All three equations use weight in kilograms, height in centimeters and age in years. Imperial entries are converted first (1 lb = 0.4536 kg, 1 in = 2.54 cm).
| Formula | Men | Women |
|---|---|---|
| Mifflin-St Jeor (1990) | 10W + 6.25H − 5A + 5 | 10W + 6.25H − 5A − 161 |
| Harris-Benedict, revised by Roza and Shizgal (1984) | 88.362 + 13.397W + 4.799H − 5.677A | 447.593 + 9.247W + 3.098H − 4.330A |
| Katch-McArdle | 370 + 21.6 × LBM, where LBM = W × (1 − body fat % ÷ 100) | |
Worked example
A 30-year-old man, 180 cm tall, weighing 80 kg with 18% body fat:
- Mifflin-St Jeor: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal
- Harris-Benedict: 88.362 + 1,071.76 + 863.82 − 170.31 = 1,854 kcal
- Katch-McArdle: lean mass = 80 × 0.82 = 65.6 kg, so 370 + 21.6 × 65.6 = 1,787 kcal
If he is moderately active, his daily calorie needs with Mifflin-St Jeor are about 1,780 × 1.55 = 2,759 kcal.
Activity multipliers
| Activity level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise or sport 1–3 days a week |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week |
| Very active | 1.725 | Hard exercise 6–7 days a week |
| Extra active | 1.9 | Very hard training or a physical job |
Which formula should you trust? Studies comparing predicted and measured resting metabolism find Mifflin-St Jeor is the most reliable for most healthy adults. Harris-Benedict tends to run slightly higher. Katch-McArdle ignores age and sex and works best when your body fat percentage comes from a good measurement such as a DEXA scan. These results are estimates for healthy adults and are not medical advice.
Frequently asked questions
What is BMR?
Basal metabolic rate (BMR) is the number of calories your body needs at complete rest to keep you alive: breathing, circulation, temperature control and cell repair. For most people it makes up 60 to 70% of the calories burned each day.
Which BMR formula is most accurate?
For most adults the Mifflin-St Jeor equation is the most accurate of the common formulas and is the one recommended by many dietitians. Katch-McArdle can be better for lean, muscular people if you know your body fat percentage accurately.
What is the Mifflin-St Jeor equation?
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 instead of + 5 for women. A 30-year-old man who weighs 80 kg and is 180 cm tall has a BMR of 1,780 kcal per day.
What is the difference between BMR and TDEE?
BMR is what you burn at rest. TDEE (total daily energy expenditure) adds daily movement and exercise. It is estimated by multiplying BMR by an activity factor from 1.2 (sedentary) to 1.9 (extra active).
Why does Katch-McArdle need body fat?
It estimates BMR from lean body mass (your weight minus fat mass) instead of total weight, height, age and sex. Lean tissue burns most of the energy at rest, so the formula needs your body fat percentage to work out lean mass.
Should I eat less than my BMR to lose weight?
Usually no. Eating well below your BMR for long periods makes it hard to get enough nutrients and is difficult to sustain. A moderate deficit from your TDEE (often around 500 kcal a day) is a more common approach. Ask a doctor or dietitian for personal advice.