BMR Calculator
Estimate your basal metabolic rate in kcal per day from age, sex, height, and weight, using the Mifflin-St Jeor, Revised Harris-Benedict, or Katch-McArdle equation, with a daily calorie table for five activity levels.
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Basal metabolic rate
BMR result
Daily calorie needs by activity level
| Activity level | Multiplier | kcal/day |
|---|---|---|
| Sedentary: little or no exercise | 1.2 | - |
| Light: exercise 1-3 days a week | 1.375 | - |
| Moderate: exercise 3-5 days a week | 1.55 | - |
| Active: hard exercise 6-7 days a week | 1.725 | - |
| Very active: hard exercise plus a physical job | 1.9 | - |
BMR is the energy your body uses at complete rest, usually measured after a 12-hour fast. The equations estimate it to within about 100-200 kcal of each other. This is a general estimate, not a medical diagnosis.
Updated: kcal per dayOn this page
The BMR calculator estimates your basal metabolic rate, the calories your body burns at complete rest to keep your organs working, from age, sex, height, and weight. It runs on the Mifflin-St Jeor equation from 1990 by default, the formula research most often finds most accurate for normal-weight adults, and you can switch to Revised Harris-Benedict or Katch-McArdle to compare results.
How to use the BMR calculator
- Pick Male or Female. Mifflin-St Jeor adds 5 to the result for men and subtracts 161 for women.
- Enter your age in years. The tool accepts 15 to 80, the range the Mifflin-St Jeor study validated.
- Enter height and weight in Metric (cm and kg) or US customary (ft, in, and lb) using the Unit system selector.
- Choose an equation in the Equation dropdown. Selecting Katch-McArdle reveals a Body fat field, because that formula works from lean body mass.
- Read the result panel. It updates with every change you make, beside the form on desktop and below it on small screens, so the BMR number always matches the values in the Entered values row. There is no Calculate button to press.
What the result shows
The result panel shows your BMR in kcal/day with a kJ/day equivalent (1 kcal = 4.184 kJ), the equation used, and a summary of the entered values. The panel refreshes as you edit any field, so what you see always belongs to the values listed in the Entered values row. Below that, a table lists daily calorie needs for five activity levels, from Sedentary with a 1.2 multiplier to Very active with 1.9. Each row multiplies your BMR by that activity factor, so a 1,649 kcal/day BMR becomes 2,556 kcal/day at the Moderate 1.55 level.
Use the Copy result button to grab the whole panel, BMR, equation, and activity table, in one clipboard write.
The three equations
All three formulas take weight W in kg, height H in cm, and age A in years. Katch-McArdle needs lean body mass (LBM) instead, calculated from body fat: LBM = W x (1 – body fat / 100).
| Equation | Men | Women |
|---|---|---|
| Mifflin-St Jeor (1990) | 10W + 6.25H – 5A + 5 | 10W + 6.25H – 5A – 161 |
| Revised Harris-Benedict | 13.397W + 4.799H – 5.677A + 88.362 | 9.247W + 3.098H – 4.330A + 447.593 |
| Katch-McArdle | 370 + 21.6 x LBM | 370 + 21.6 x LBM |
Worked examples
Take a 30-year-old man, 175 cm, 70 kg. Mifflin-St Jeor gives 10 x 70 + 6.25 x 175 – 5 x 30 + 5 = 1,649 kcal/day, the number the page shows the moment it loads. The same inputs on Revised Harris-Benedict give 13.397 x 70 + 4.799 x 175 – 5.677 x 30 + 88.362 = 1,696 kcal/day, about 47 kcal higher. A woman with the same measurements gets 1,483 kcal/day on Mifflin-St Jeor because the sex constant is -161 instead of +5.
Katch-McArdle changes the input set. The same 70 kg man at 20% body fat has 56 kg of lean mass, so his BMR is 370 + 21.6 x 56 = 1,580 kcal/day.
Limits and notes
- Age is capped at 15 to 80, the range Mifflin-St Jeor was validated on. Height must be 50 to 250 cm (roughly 1 ft 8 in to 8 ft 2 in) and weight 20 to 350 kg (44 to 770 lb).
- Body fat is accepted from 3% to 60% and only matters for Katch-McArdle.
- Formulas disagree by about 100 to 200 kcal between individuals, so treat the number as an estimate, not a measurement.
- Lab BMR is measured awake, after a 12-hour fast, lying still. Resting metabolic rate includes digestion and runs about 10% higher.
- Prolonged starvation can lower BMR by up to 30% as the body conserves energy.
- Results are a general reference for adults, not a medical diagnosis or a plan for children, pregnancy, or medical conditions.