BMR
Calculate Basal Metabolic Rate for calorie planning
These calculators provide general information only and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How to use BMR
- 1Select sex and unit system. Sex sets the constant term in the equation.
- 2Enter age, height and weight. Age affects basal metabolism more than most people expect.
- 3Read your daily basal calorie need, then apply an activity factor to estimate total daily energy expenditure.
How basal metabolic rate is calculated
Mifflin-St Jeor: men BMR = 10W + 6.25H − 5A + 5, women BMR = 10W + 6.25H − 5A − 161Basal metabolic rate is the energy needed to keep your heart beating, lungs working and body temperature stable while awake, fasted and resting in a neutral environment. It usually accounts for 60% to 75% of total daily energy expenditure. This tool uses the Mifflin-St Jeor equation by default, which is among the most accurate predictive formulas for the general population. W is weight in kilograms, H height in centimetres and A age in years.
Other common options include the revised Harris-Benedict equation, which dates back to 1919 and tends to overestimate modern adults by 5% to 10%, and Katch-McArdle, which is the most accurate when you know your body fat percentage. Prediction error is typically within plus or minus 10%, and individual variation comes mostly from muscle mass, genetics and hormones. Treat BMR as the starting point for a food plan rather than a laboratory measurement; indirect calorimetry or doubly labelled water is needed for that.
| Activity level | Factor | Description | Example (BMR 1,500) |
|---|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise | 1,800 kcal |
| Lightly active | 1.375 | Light exercise 1–3 days a week | 2,063 kcal |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week | 2,325 kcal |
| Very active | 1.725 | Hard exercise 6–7 days a week | 2,588 kcal |
Activity factors and total daily energy expenditure
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the minimum energy needed to stay alive at complete rest. TDEE adds everyday movement, exercise and the cost of digesting food: TDEE = BMR × activity factor. Plan your intake from TDEE, not BMR, or you will end up eating far too little.
Why do different formulas give different numbers?
They were fitted to different populations in different eras. Mifflin-St Jeor was derived in 1990 and suits modern adults well. Harris-Benedict dates from 1919, revised in 1984, and overestimates by roughly 5% to 10%. Katch-McArdle needs body fat percentage but is the most accurate when you have it. Differences are usually within 100 to 200 kcal, so pick one and stay consistent.
Does dieting slow down metabolism?
It does. A sustained large deficit triggers adaptive thermogenesis: the body trims non-essential movement and thyroid output, and basal metabolism can drop 10% to 20%, with part of the drop persisting after you eat normally again. Keep the deficit to 300 to 500 kcal per day and combine it with resistance training and adequate protein to limit the effect.
How much should I eat to lose fat?
Work out your TDEE and subtract 300 to 500 kcal, which corresponds to roughly 0.3 to 0.5 kg per week. Do not eat below your BMR, and stay above about 1,200 kcal a day for women and 1,500 for men. Two or three resistance sessions a week plus 1.6 to 2.2 grams of protein per kilogram of bodyweight will help you keep muscle.