BMR calculator with four formulas
The calories your body burns at rest, with Mifflin-St Jeor, Harris-Benedict, Katch-McArdle and Cunningham, and how far they differ.
Calculator inputs
Results
Enter your values and press “Calculate” to see the result.
| Formula | kcal per day |
|---|---|
| Mifflin-St Jeor | 1,743 |
| Harris-Benedict (Roza-Shizgal) | 1,816 |
See the working step by step
- Mifflin-St Jeor = 1,743; revised Harris-Benedict = 1,816
- Sedentary (×1.2) = 2,091; moderate (×1.55) = 2,700.88; very active (×1.9) = 3,310.75 kcal a day
In short
- What it calculates
- The calories your body burns at rest, with Mifflin-St Jeor, Harris-Benedict, Katch-McArdle and Cunningham, and how far they differ.
- Formula used
Mifflin-St Jeor: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (male) or − 161 (female)- Example
- Example 1. A 35-year-old man.
BMR calculator
Your basal metabolic rate (BMR) is the calories your body burns at complete rest just to stay alive: breathing, pumping blood, keeping its temperature. It is usually 60% to 75% of everything you burn in a day, and the starting point of any calorie plan.
Enter your weight, height, age and sex, and pick the formula. The calculator gives the result with each one, the average and the gap between them, so you see the real margin of error. If you know your body-fat percentage, it also adds the lean-mass-based formulas. Everything runs in your browser.
How it works
Each formula is a regression obtained by measuring resting energy expenditure in groups of people. Mifflin-St Jeor (1990) uses weight, height, age and sex and is the most reliable for today’s general population. Harris-Benedict, from 1919, was revised in 1984 (Roza and Shizgal) and tends to give slightly higher values.
Katch-McArdle and Cunningham use lean mass (weight without fat), because it is the tissue that burns the most. They are more accurate in very muscular or very fat people, but need your body-fat percentage with some accuracy.
Formula
Mifflin-St Jeor: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (male) or − 161 (female)
Revised Harris-Benedict, male: 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
Revised Harris-Benedict, female: 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age
Lean mass = weight × (1 − body fat % ÷ 100)
Katch-McArdle: 370 + 21.6 × lean mass Cunningham: 500 + 22 × lean mass
Worked example
Example 1. A 35-year-old man.
At 80 kg and 178 cm, Mifflin-St Jeor gives 10 × 80 + 6.25 × 178 − 5 × 35 + 5 = 1,742.5 kcal a day, about 73 an hour. Revised Harris-Benedict gives 1,816 kcal and the average of the two is 1,779.
Example 2. A 30-year-old woman.
At 62 kg and 165 cm, Mifflin-St Jeor gives 10 × 62 + 6.25 × 165 − 5 × 30 − 161 = 1,340.25 kcal a day.
Example 3. With body-fat percentage.
The man from example 1 at 18% body fat has 65.6 kg of lean mass and Katch-McArdle gives 1,787 kcal, very close to Mifflin. At 30% body fat, the same formula would drop to 1,580 kcal: body composition matters more than weight.
Explanation
What basal metabolic rate is
It is the energy the body uses at rest, fasted and in a comfortable environment, just to sustain vital functions. It does not include movement, exercise or digestion.
Which formula to choose
- **Mifflin-St Jeor**: the best general choice; recommended by the Academy of Nutrition and Dietetics for adults.
- **Revised Harris-Benedict**: widely used, slightly higher.
- **Katch-McArdle and Cunningham**: if you know your body-fat percentage, especially if very muscular or very overweight.
None is exact: individual variation in metabolism is ±10% or more.
What affects BMR
- **Lean mass**: more muscle, more expenditure.
- **Age**: it falls gradually.
- **Sex**: on average higher in men, because of more lean mass.
- **Genetics, thyroid hormones, pregnancy and illness**.
From BMR to total expenditure
Daily expenditure is BMR multiplied by an activity factor (1.2 to 1.9) plus the thermic effect of food. The energy-expenditure (TDEE) calculator makes that conversion.
Common mistakes
- Eating below your basal rate for long periods: it causes muscle loss and is not advisable without supervision.
- Taking the figure as exact.
- Entering weight in pounds or height in inches without converting.
- Overestimating activity when going from BMR to total expenditure.
Limits of this calculator
- They are statistical estimates for healthy adults; they do not apply to under-15s, pregnant women or people with conditions that alter metabolism.
- It does not replace indirect calorimetry, which measures actual expenditure.
- Lean-mass formulas depend on the body-fat percentage being right.
Notice
This is an estimate and does not replace a health professional’s judgement. Talk to a doctor or dietitian before making big changes to your diet.
Frequently asked questions
What is basal metabolic rate?
The calories your body burns at complete rest to maintain vital functions. It is most of your daily expenditure.
Which formula is best?
Mifflin-St Jeor is the most reliable for the general population. If you know your body-fat percentage, Katch-McArdle and Cunningham may be more accurate.
How many calories should I eat below my BMR?
None: eating below BMR for long periods is not advised without professional supervision. Set the deficit on total expenditure, not on BMR.
How can I raise my BMR?
By gaining muscle through strength training, eating enough protein and sleeping well. The effects of “boosters” are small.
Why do the formulas differ?
Because they were derived from different populations and methods. That is why the range is shown: reality is usually between them, with ±10% individual variation.
Does it work for pregnant women or children?
No. They are formulas for healthy adults; in pregnancy, breastfeeding or childhood, needs are different.
Is it the same as daily calorie burn?
No. Daily expenditure (TDEE) adds physical activity and the thermic effect of food, and is always higher than BMR.
Is my data sent to a server?
No. The calculation runs in your browser.
Sources and references
The formula behind this calculator is not ours. These are the sources it comes from, in APA 7 format, in case you want to go to the original or cite them in your own work.
- Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition, 51(2), 241–247. https://doi.org/10.1093/ajcn/51.2.241 https://doi.org/10.1093/ajcn/51.2.241 The Mifflin-St Jeor equation.
- Roza, A. M., & Shizgal, H. M. (1984). The Harris Benedict equation reevaluated: Resting energy requirements and the body cell mass. The American Journal of Clinical Nutrition, 40(1), 168–182. https://doi.org/10.1093/ajcn/40.1.168 https://doi.org/10.1093/ajcn/40.1.168 The revised Harris-Benedict coefficients.
- Cunningham, J. J. (1980). A reanalysis of the factors influencing basal metabolic rate in normal adults. The American Journal of Clinical Nutrition, 33(11), 2372–2374. https://doi.org/10.1093/ajcn/33.11.2372 https://doi.org/10.1093/ajcn/33.11.2372 The lean-mass-based formula.
Need to calculate something else?
These tools are often used alongside this calculator.
TDEE
Your total daily calorie burn for your activity level, and the calories to lose fat or gain weight, with…
Calories
The calories you need a day to lose fat, maintain or build muscle, and the split of protein, fat and…
Protein
The grams of protein you need for your weight and profile: low activity, active, strength or fat loss, or…
BMI
Your body mass index, your WHO category, the healthy weight range for your height and the waist-to-height…
Body fat
US Navy method estimate from your body circumferences.
Ideal weight
Four classic formulas plus the healthy range from BMI.