BMR Calculator
Basal metabolic rate from the Mifflin-St Jeor, Harris-Benedict and Katch-McArdle equations, side by side.
About you
Filled in with example values. Replace them with your own.
Optional
Adds the Katch-McArdle equation, which uses lean body mass. Only as good as the body fat measurement.
Results update as you type.
Result
BMR (Mifflin-St Jeor): about 1,780 kcal a day
Basal metabolic rate
1,780kcal a day
An estimate, not medical advice. BMR equations predict the average for people of your age, sex and size; your own BMR can be noticeably higher or lower. They were not made for pregnancy, children or medical conditions that affect metabolism, and only a clinical measurement gives your actual BMR.
- Mifflin-St JeorMifflin, St Jeor et al., 1990
- 1,780 kcal
- Harris-Benedict (revised)Roza and Shizgal, 1984
- 1,854 kcal
- Difference between equations
- 74 kcal
The equations side by side (kcal a day)
BMR is the minimum at rest. The calories you use in a day are higher: see the TDEE Calculator for your activity level.
How it’s calculated
Mifflin-St Jeor
10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 1,780 kcal
Important
This calculator gives a general estimate from a published formula. It is not a diagnosis and not medical advice, and it cannot take your health, medicines or history into account. BMR equations predict an average; only a clinical measurement gives your actual BMR.For advice about your weight, diet or health, talk to a doctor or a registered dietitian. See theDisclaimer.
How the BMR calculator works
Basal metabolic rate (BMR) is the energy, in kilocalories (kcal), that your body uses in a day at complete rest. It cannot easily be measured at home, so it is estimated from equations fitted to measurements of many people.
The calculator shows the Mifflin-St Jeor equation first, with the revised Harris-Benedict equation alongside. If you know your body fat percentage, it also shows Katch-McArdle, which uses lean body mass instead of sex and age.
The formulas
Mifflin-St Jeor (1990)
Men: 10 × kg + 6.25 × cm − 5 × age + 5
Women: 10 × kg + 6.25 × cm − 5 × age − 161
Harris-Benedict, revised by Roza and Shizgal (1984)
Men: 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age
Women: 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age
Katch-McArdle
370 + 21.6 × lean body mass (kg)
Lean body mass = weight × (1 − body fat %). 1 kcal = 4.184 kJ.
Worked examples
- A man, 30, 180 cm, 80 kg: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 =1,780 kcal a day (Mifflin-St Jeor). Harris-Benedict gives 1,854 kcal; at 15% body fat, Katch-McArdle gives 370 + 21.6 × 68 = 1,839 kcal.
- A woman, 25, 165 cm, 60 kg: 10 × 60 + 6.25 × 165 − 5 × 25 − 161 = 1,345 kcal a day.
Limitations
- The equations predict an average. Your own BMR can be noticeably higher or lower.
- They were developed from adults and are not meant for children, pregnancy or illness that affects metabolism.
- Katch-McArdle is only as accurate as the body fat percentage you enter.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the energy your body uses at complete rest: breathing, circulation, keeping warm. TDEE (total daily energy expenditure) adds everything you do in a day, from walking to exercise, so it is always higher. The TDEE Calculator multiplies BMR by an activity level.
Which equation is the most accurate?
None is exact for an individual; each predicts the average for people like you. Mifflin-St Jeor is shown first because it is the newer of the two general equations and is widely used. Seeing all of them side by side shows how much the estimate depends on the formula.
When should I use Katch-McArdle?
Only if you have a reasonably reliable body fat measurement. It works from lean body mass rather than sex and age, so it can suit people with much more or less muscle than average. An inaccurate body fat figure makes it inaccurate too.
Why does the calculator ask for sex?
Both Mifflin-St Jeor and Harris-Benedict give different results for men and women: Mifflin-St Jeor changes one constant, Harris-Benedict uses separate equations. If neither option fits you, Katch-McArdle with a body fat measurement does not use sex.
Can I use it for children?
No. The equations were developed from adults, so the calculator accepts ages of 18 and over.