What is BMR?
Basal metabolic rate (BMR) is the number of calories your body burns in a day at complete rest: breathing, circulating blood, keeping warm and repairing cells. It accounts for 60–70% of the energy most people use. Everything you do on top — walking, working, exercising — adds to it, and that total is your daily energy expenditure.
Formulas
Mifflin-St Jeor: 10 × weight + 6.25 × height − 5 × age + 5 (men) or − 161 (women)Harris-Benedict (1984): 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age (men); 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age (women)Katch-McArdle: 370 + 21.6 × lean body mass, where lean mass = weight × (1 − body fat ÷ 100)
Worked example
A 30-year-old man who is 170 cm tall and weighs 70 kg has a BMR of about 1,618 kcal by the Mifflin-St Jeor formula. If he exercises three to five days a week, he needs about 2,507 kcal a day to keep his weight steady.
How to use the BMR calculator
- Enter your figures: age, height and weight. Body fat % is optional and counts as zero when left empty.
- Read the result. It updates as you type, so there is no button to press.
- Try other numbers to compare scenarios. Reset brings back the example values.
Getting it right
- Mifflin-St Jeor is the most accurate of the three for most adults in studies. Katch-McArdle can be better for lean, muscular people if you know your body fat percentage.
- To lose about half a kilogram a week, eat around 500 calories a day below your daily need — but not below your BMR without medical advice.
- Any formula is an estimate within about 10%. Track your weight for two to three weeks and adjust.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is what you burn at complete rest. TDEE (total daily energy expenditure) adds everything else you do in a day; it is BMR multiplied by an activity factor, shown in the table.
What is a normal BMR?
For most adults it falls between about 1,200 and 2,000 calories a day. It is higher in men, taller and heavier people, and people with more muscle, and it falls slowly with age.
Can I raise my BMR?
Building muscle raises it a little, because muscle uses more energy at rest than fat. Very low-calorie diets tend to lower it.