Calculate your basal metabolic rate — the calories your body burns at complete rest — with the Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle formulas, plus daily energy at five activity levels.
How BMR is calculated
Basal metabolic rate is the energy your body burns at complete rest — awake, fasted, in a neutral-temperature room. It is usually 60–75% of what you burn in a day. The headline figure uses the Mifflin-St Jeor equation, which validation studies have found the most accurate population formula for adults:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
The revised Harris-Benedict equation (Roza & Shizgal, 1984) is shown for comparison because many diet plans still quote it. If you know your body fat percentage, the Katch-McArdle formula (370 + 21.6 × lean body mass in kg) ignores sex and age and is often closer for lean or very muscular people.
From BMR to daily calories
| Activity level | Factor | Who it fits |
|---|---|---|
| Sedentary | 1.2 | Desk work, 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 | Physical job plus daily training, or two sessions a day |
BMR × factor = total daily energy expenditure (TDEE), the calories that keep your weight stable. The calorie calculator turns that into targets for losing or gaining weight.
This calculator is for general information only and is not medical advice. Results are estimates based on population formulas; speak to a doctor or registered dietitian before changing your diet, training or medication.
Frequently asked questions
What is a normal BMR?
Roughly 1,200–1,500 kcal/day for adult women and 1,500–1,900 kcal/day for adult men, varying with size, age and muscle mass. Taller, heavier and younger people burn more at rest.
Which BMR formula is most accurate?
Mifflin-St Jeor for most adults — it predicts within 10% for about 70–80% of people. Katch-McArdle can be better if you know your body fat percentage accurately.
Is BMR the same as resting metabolic rate (RMR)?
Nearly. RMR is measured under less strict conditions and runs about 10% higher than BMR; calculators use the two terms loosely.
Should I eat at my BMR to lose weight?
No. BMR is your energy at complete rest; you burn more just by living. Set a deficit from your total daily expenditure (BMR × activity factor) and avoid going below about 1,200 kcal (women) or 1,500 kcal (men) without medical supervision.
Why does my BMR fall with age?
Lean mass declines and hormone levels change, so resting energy use drops roughly 1–2% per decade after the twenties. Strength training slows the fall.
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