BMR Calculator
What basal metabolic rate means
Your basal metabolic rate is the energy your body needs at complete rest just to keep you alive: breathing, circulation, temperature regulation, brain activity and cell repair. For most people it represents 60–70% of the calories they burn in a day, even though it involves no movement at all.
The formula used
This calculator applies the Mifflin-St Jeor equation, published in 1990 and recommended by many dietetic organisations as the most accurate of the classic equations for healthy 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
Worked examples
- A man aged 30, 70 kg, 175 cm: 700 + 1,093.75 − 150 + 5 = 1,649 kcal/day.
- A woman aged 25, 60 kg, 165 cm: 600 + 1,031.25 − 125 − 161 = 1,345 kcal/day.
What makes BMR higher or lower
- Body size: a larger body has more tissue to maintain, so weight and height both raise BMR.
- Muscle mass: muscle uses more energy at rest than fat. Two people with the same weight can have different BMRs; the formula cannot see this difference.
- Age: BMR declines slowly with age, largely because of muscle loss — each extra decade lowers the estimate by 50 kcal.
- Sex: at the same size, men usually have more lean mass, hence the 166 kcal difference between the two equations.
- Dieting: prolonged calorie restriction reduces energy expenditure a little more than weight loss alone would explain.
How to use your BMR
BMR is not the number of calories you should eat — it is the floor. To find your actual daily needs, multiply it by your activity level with the daily calorie (TDEE) calculator. Eating below your BMR for long periods is generally not recommended without medical supervision.
Frequently Asked Questions
Should I eat my BMR in calories to lose weight?
No. BMR is what you burn lying still all day. Your real needs (TDEE) are higher; a moderate deficit below TDEE is enough to lose weight and is easier to sustain.
Why is BMR different for men and women?
At the same weight and height, men have on average more muscle and less fat, and muscle consumes more energy at rest. The equations reflect this with a different constant.
Can I increase my BMR?
Building muscle through strength training raises it modestly. Staying active and eating enough protein also helps limit the drop in metabolism during a diet.