Calculators
BMR Calculator
Estimate your basal metabolic rate, the calories your body uses at complete rest, with the Mifflin–St Jeor equation.
About the BMR Calculator
The BMR Calculator estimates your basal metabolic rate, the calories your body uses at complete rest: from your age, sex, weight and height, in kg and cm or pounds and feet. It compares two well-known formulas and shows what your BMR means across activity levels.
What you can do with the BMR Calculator
- Two formulas: Compares Mifflin–St Jeor and Harris–Benedict.
- Metric or imperial: kg and cm, or pounds and feet.
- Activity levels: See what your BMR means for different activity levels.
- Plain explanation: What BMR is and how to use it.
Two formulas
The main figure uses the Mifflin–St Jeor equation, published in 1990 and widely considered one of the more accurate formulas for healthy adults. The revised Harris–Benedict equation, older and still common, usually gives a slightly higher number; seeing both gives a sense of the range.
What BMR means day to day
For most people BMR is the majority of the calories they burn each day, often around 60–70%. Activity and digesting food make up the rest; the activity bars and the Calorie Needs (TDEE) tool cover that part.
Why it's only an estimate
Two people with the same height, weight and age can have different metabolic rates because of muscle mass, genetics and health. Formulas are typically within about 10% for most people. For medical questions, talk to a doctor.
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Frequently Asked Questions
What's the difference between BMR and TDEE?
BMR is what you burn at complete rest. TDEE adds the calories burned through daily activity and exercise.
Can I use pounds and feet?
Yes. Tap "lb · ft/in" to enter weight in pounds and height in feet and inches.
Is this a medical measurement?
No. It's a formula-based estimate. Clinics can measure metabolic rate directly if you need an exact figure.
Why is my BMR lower than I expected?
BMR covers only breathing, circulation and other functions at complete rest, not walking, work or exercise. It is usually the largest part of daily energy use, but your total needs are higher. The activity bars multiply BMR by 1.2 to 1.9 to estimate a full day.
How many calories should I eat to lose weight?
A common rule of thumb is that a deficit of about 500 kcal a day below your total daily needs, not your BMR, leads to roughly 0.5 kg loss a week. Needs vary from person to person, so check with a doctor or dietitian before a big change.
Should I eat fewer calories than my BMR?
Eating below BMR for long periods is generally not recommended without medical supervision, because it can be hard to meet nutrient needs. BMR is a floor estimate of what your body uses at rest. A doctor or registered dietitian can advise on a safe intake.
Why does BMR go down as I get older?
In the Mifflin-St Jeor formula, age reduces BMR by 5 kcal a day for every year, mostly reflecting the loss of muscle with age. A 70 kg, 175 cm man has an estimated BMR of about 1,649 kcal at 30 and about 1,549 kcal at 50.
Why is BMR different for men and women?
Men usually have more muscle for the same weight and height, which uses more energy. Mifflin-St Jeor adds 5 for men and subtracts 161 for women, a gap of 166 kcal a day for the same age, weight and height. Choose Male or Female at the top.
Which BMR formula is more accurate?
Mifflin-St Jeor is generally considered the more accurate of the two for most adults, which is why it is the main result here. The revised Harris-Benedict figure is shown alongside for comparison. Both are estimates, and real metabolism can differ by around 10%.
What does "Per hour at rest" mean?
It is your daily BMR divided by 24, showing roughly how many calories your body uses each hour while resting. For a BMR of 1,649 kcal a day, that is about 69 kcal an hour. It gives a sense of scale for snacks and exercise.
What age and weight ranges does the calculator accept?
Age can be set from 15 to 90 years, weight from 30 to 200 kg (66 to 440 lb), and height from 120 to 220 cm or 4 to 7 feet. The formulas were developed for adults, so results for teenagers are rougher estimates.
Read the guide
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