FitCalculationBMR (Basal Metabolic Rate) is the number of calories your body needs to function at complete rest. It accounts for about 60-75% of the total calories you burn each day, depending on activity level.
BMR Calculator
Estimate the calories your body burns at rest using the Mifflin-St Jeor equation, with a Katch-McArdle option when body composition is known.
What this calculates
Resting energy is estimated from weight, height, age and sex via Mifflin-St Jeor, or from lean body mass via Katch-McArdle when body fat percentage is supplied.
What is BMR?
The Mifflin-St Jeor equation replaced the older Harris-Benedict formula in 1990. It is more accurate for modern populations and is the equation used by this calculator. When body fat percentage is provided, the Katch-McArdle formula is shown as an alternative because it accounts for lean body mass.
BMR is the starting point for every TDEE and calorie calculation. Your actual daily burn is BMR multiplied by an activity factor, which is what the TDEE calculator shows. To know both numbers, start with BMR.
How to calculate BMR
Mifflin-St Jeor equation
For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) + 5
For women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) − 161
The formula uses metric units internally. Imperial inputs (feet, inches, pounds) are converted before the equation runs, so results are identical regardless of the unit system you select. Published in 1990, it replaced the older Harris-Benedict formula.
Katch-McArdle equation
BMR = 370 + (21.6 × lean mass in kg)
Lean mass is your body weight minus fat mass. If body fat is 20% and weight is 80 kg, lean mass is 64 kg and the Katch-McArdle estimate is 370 + (21.6 × 64) = 1,752 kcal/day. The Katch-McArdle guide explains when this formula is more accurate.
BMR vs TDEE
BMR is calories at rest; TDEE is calories over a full day, including food digestion, walking, and exercise. BMR typically makes up 60-75% of TDEE, depending on activity level.
A sedentary person's TDEE is roughly BMR × 1.2. A very active person's TDEE can be BMR × 1.9 or higher. For your full daily estimate, use the TDEE calculator, which multiplies this BMR by an activity factor, or read the BMR vs TDEE guide.
BMR FAQ
What is a good BMR?
A good BMR is one that, when multiplied by your activity level, helps you reach your goal. There is no single "good" value — it varies by weight, height, age, and sex. A 25-year-old woman who is 5'4" and 130 lb has a lower BMR than a 25-year-old man who is 6'0" and 180 lb, even if they share a lifestyle. To see what your BMR means for daily eating, use the TDEE calculator.
Is higher BMR better?
A higher BMR means your body burns more calories at rest, which can make weight management easier. Building muscle increases BMR because muscle tissue is metabolically active. However, BMR is partly genetic and partly physiological — it is not a goal you can optimize beyond reasonable health.
Can I increase my BMR?
Muscle mass, strength training, adequate sleep, and not crash-dieting all support a healthy BMR. Your age and sex are not choices, but activity level and body composition partly are. The BMR calculator gives you a baseline to work from. If you know your body fat percentage, the body fat calculator can give you the lean mass needed for the Katch-McArdle estimate below.
What factors affect BMR?
BMR is driven primarily by lean body mass, followed by age, sex, and genetics. Two people of the same weight can have different BMRs depending on how much is muscle versus fat, which is why the Katch-McArdle option on this calculator can give a different answer from Mifflin-St Jeor. Weight and height set the scale the equations work from.
Is Mifflin-St Jeor better than Harris-Benedict?
Yes, the Mifflin-St Jeor equation is more accurate than the older Harris-Benedict formula for most people today. It was published in 1990 with updated population data and consistently outperformed Harris-Benedict in validation studies. Read the comparison guide for the full picture.
Why is BMR different from TDEE?
BMR measures calories burned at complete rest; TDEE adds the calories from walking, thinking, digesting food, and exercise over a full day. BMR typically makes up 60–75% of TDEE. For your total daily estimate, use the TDEE calculator, which multiplies this BMR by an activity factor. The guide to BMR vs TDEE explains the difference in depth.
Example: BMR at different weights and body-fat levels
For a 30-year-old, 180 cm (5 ft 11 in) male, BMR at three weights and two body-fat percentages — all computed from the Mifflin-St Jeor and Katch-McArdle equations:
| Weight | Body fat | Mifflin-St Jeor | Katch-McArdle |
|---|---|---|---|
| 70 kg (154 lb) | — | 1680 kcal | — |
| 70 kg (154 lb) | 15 % | 1680 kcal | 1655 kcal |
| 70 kg (154 lb) | 25 % | 1680 kcal | 1504 kcal |
| 80 kg (176 lb) | — | 1780 kcal | — |
| 80 kg (176 lb) | 15 % | 1780 kcal | 1839 kcal |
| 80 kg (176 lb) | 25 % | 1780 kcal | 1666 kcal |
| 90 kg (198 lb) | — | 1880 kcal | — |
| 90 kg (198 lb) | 15 % | 1880 kcal | 2022 kcal |
| 90 kg (198 lb) | 25 % | 1880 kcal | 1828 kcal |