BMR Calculator
Estimates basal metabolic rate with the Mifflin-St Jeor equation from weight, height, age and sex.
Recent
Formula
How the calculation works
The Mifflin-St Jeor equation estimates basal metabolic rate, the energy a body burns at complete rest, from four simple inputs: weight in kilograms, height in centimetres, age in years, and sex.
It works by scaling body mass at 10 kcal per kilogram, adding 6.25 kcal per centimetre of height, and subtracting 5 kcal for each year of age, because resting energy tends to fall as people get older.
Men then add 5 to the result and women subtract 161, which reflects the average difference in lean mass; for a 70 kg, 170 cm, 30-year-old man this gives about 1618 kcal per day.
Common mistakes
- Do not mix units: this equation expects kilograms and centimetres, so pounds or inches must be converted first or the result will be wildly wrong.
- Remember that BMR is the resting floor, not daily calorie needs; multiplying by an activity factor is a separate step this calculator does not perform.
- Sex is not optional here: choosing the wrong option shifts the result by roughly 166 kcal, a meaningful gap when planning meals.
When to use it
- Use the BMR as the starting point for a daily calorie plan, then scale it by an activity multiplier for sedentary, moderate, or active days.
- Use it with a clinician or dietitian when setting a safe energy target for weight loss, weight gain, or maintenance.
Worked example
For a 70 kg, 170 cm, 30-year-old man the Mifflin-St Jeor BMR is about 1618 kcal per day.
Common questions
What is BMR and how is it different from daily calorie needs?
BMR is the energy burned at complete rest; daily needs are higher because you also multiply it by an activity factor for movement, exercise and digestion.
Why do men and women get different results?
The formula adds 5 for men and subtracts 161 for women to reflect the average difference in lean body mass, so the same weight, height and age can give two different BMR values.
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