How to use this BMR calculator
- Choose your units and enter your sex and age.
- Enter your height and weight. The result updates as you type.
- Optional: open Equation & body fat to switch equations or add your body fat percentage for the Katch-McArdle estimate.
- Read the activity table to see estimated daily calories at five activity levels.
BMR formulas
In all three equations, W is weight in kilograms, H is height in centimeters and A is age in years. Results are in kilocalories (the “calories” on food labels) per day.
Mifflin-St Jeor (1990)
BMR = 10W + 6.25H − 5A + 5
BMR = 10W + 6.25H − 5A − 161
- W
- weight in kg (pounds × 0.4536)
- H
- height in cm (inches × 2.54)
- A
- age in years
Worked example
A 35-year-old woman, 5′ 5″ and 150 lb. Convert first: 150 lb × 0.4536 = 68.04 kg, and 65 in × 2.54 = 165.1 cm. Then
BMR = 10 × 68.04 + 6.25 × 165.1 − 5 × 35 − 161 = 680.4 + 1,031.9 − 175 − 161 = 1,376 calories a day.
Multiply by an activity factor to estimate total daily calories: × 1.2 (sedentary) = 1,652, or × 1.55 (moderately active) = 2,133.
Revised Harris-Benedict (Roza and Shizgal, 1984)
BMR = 88.362 + 13.397W + 4.799H − 5.677A
BMR = 447.593 + 9.247W + 3.098H − 4.330A
For the same woman: 447.593 + 9.247 × 68.04 + 3.098 × 165.1 − 4.330 × 35 = 1,437 calories a day.
Katch-McArdle (uses lean body mass)
BMR = 370 + 21.6 × LBM, where LBM = W × (1 − body fat %)
- LBM
- lean body mass in kg
If the same woman has 30% body fat, her lean mass is 68.04 × 0.7 = 47.63 kg, and BMR = 370 + 21.6 × 47.63 = 1,399 calories a day. Sex and age do not appear; they matter only through lean mass.
Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle
For typical adults the equations land close together, as this comparison for the example person shows, but they are not interchangeable at every age and size.
| Person | Mifflin-St Jeor | Revised Harris-Benedict | Difference |
|---|---|---|---|
| Woman, 35, 5′ 5″, 150 lb | 1,376 | 1,437 | 4.4% |
| Man, 35, 5′ 5″, 150 lb | 1,542 | 1,593 | 3.3% |
| Woman, 60, 5′ 5″, 150 lb | 1,251 | 1,328 | 6.2% |
- Mifflin-St Jeor was derived in 1990 from 498 healthy adults aged 19 to 78, both normal-weight and obese, whose resting energy expenditure was measured by indirect calorimetry. The authors found the original 1919 Harris-Benedict equations overestimated measured values by about 5%.
- Revised Harris-Benedict updates the 1919 equations using the original data plus additional subjects. Roza and Shizgal reported that the equations estimate resting energy expenditure of normally nourished people with a precision of about ±14%, but are unreliable in malnourished patients.
- Katch-McArdle uses lean body mass instead of weight, height, age and sex. Because it ignores age and sex, it is only as good as the body fat number you give it, and body fat estimates vary with the method used. Try the body fat calculator for an estimate.
BMR chart by weight and age
Mifflin-St Jeor BMR in calories per day. Find the closest weight and age; each 1 inch of height adds about 16 calories (6.25 × 2.54).
| Weight | Age 25 | Age 35 | Age 45 | Age 55 | Age 65 |
|---|---|---|---|---|---|
| 120 lb | 1,274 | 1,224 | 1,174 | 1,124 | 1,074 |
| 140 lb | 1,365 | 1,315 | 1,265 | 1,215 | 1,165 |
| 160 lb | 1,456 | 1,406 | 1,356 | 1,306 | 1,256 |
| 180 lb | 1,546 | 1,496 | 1,446 | 1,396 | 1,346 |
| 200 lb | 1,637 | 1,587 | 1,537 | 1,487 | 1,437 |
| 220 lb | 1,728 | 1,678 | 1,628 | 1,578 | 1,528 |
| Weight | Age 25 | Age 35 | Age 45 | Age 55 | Age 65 |
|---|---|---|---|---|---|
| 150 lb | 1,656 | 1,606 | 1,556 | 1,506 | 1,456 |
| 170 lb | 1,746 | 1,696 | 1,646 | 1,596 | 1,546 |
| 190 lb | 1,837 | 1,787 | 1,737 | 1,687 | 1,637 |
| 210 lb | 1,928 | 1,878 | 1,828 | 1,778 | 1,728 |
| 230 lb | 2,019 | 1,969 | 1,919 | 1,869 | 1,819 |
| 250 lb | 2,109 | 2,059 | 2,009 | 1,959 | 1,909 |
From BMR to daily calories
BMR covers only what you burn at rest. To estimate total daily energy expenditure (the calories that keep your weight steady), calculators multiply BMR by an activity factor. The values below are common multipliers used by many calculators; they are rules of thumb, not measurements.
| Activity level | Typical description | Multiplier | Example (BMR 1,376) |
|---|---|---|---|
| Sedentary | little or no exercise | × 1.2 | 1,652 |
| Lightly active | light exercise 1–3 days a week | × 1.375 | 1,892 |
| Moderately active | moderate exercise 3–5 days a week | × 1.55 | 2,133 |
| Very active | hard exercise 6–7 days a week | × 1.725 | 2,374 |
| Extra active | very hard exercise or a physical job | × 1.9 | 2,615 |
If you are unsure which level fits, start with the lower one and adjust after a few weeks. For a full daily calorie plan, see the calorie calculator and the macro calculator; to check where your weight sits for your height, use the BMI calculator.
Frequently asked questions
What is BMR?
BMR, or basal metabolic rate, is an estimate of the energy your body needs at complete rest for breathing, circulation, keeping warm and other basic functions. A 35-year-old woman who is 5′ 5″ and 150 lb has an estimated BMR of about 1,376 calories a day by the Mifflin-St Jeor equation.
Which BMR equation is most accurate?
No equation is exact for every person, but Mifflin-St Jeor is the default here because it was developed in 1990 from measured resting energy expenditure in 498 healthy adults, including people with obesity. In that study the original 1919 Harris-Benedict equations overestimated measured values by about 5%. If you know your body fat percentage reliably, Katch-McArdle is a reasonable alternative.
How many calories should I eat a day?
Start from your BMR and multiply by an activity factor to estimate the calories that maintain your current weight. For the example person, that is about 1,652 calories a day if sedentary and 2,133 if moderately active. These are starting points; weigh yourself over a few weeks and adjust. A doctor or registered dietitian can set targets for specific goals or health conditions.
What is the difference between BMR and RMR?
Strictly, BMR is energy use under basal conditions: fully rested and fasting. Resting metabolic rate (RMR), or resting energy expenditure (REE), is energy use at rest under less strict conditions. The Mifflin-St Jeor study measured and predicted REE, and the revised Harris-Benedict paper also describes resting energy expenditure. Everyday calorie tools, including this one, use the terms interchangeably, as most calculators do.
Why is BMR different for men and women?
The equations include sex as a stand-in for typical differences in body composition. Roza and Shizgal found that resting energy expenditure tracks the body’s metabolically active cell mass and does not differ between the sexes once that is accounted for. In Mifflin-St Jeor the difference is a fixed 166 calories: the same 35-year-old at 5′ 5″ and 150 lb comes out at 1,376 calories as a woman and 1,542 as a man.
Does BMR go down with age?
In these equations, yes. Mifflin-St Jeor subtracts 5 calories for every year of age, so the same body at 60 is estimated at 1,251 calories a day instead of 1,376 at 35. Roza and Shizgal found resting energy expenditure depends on metabolically active cell mass rather than age itself, which fits the lean-mass-based Katch-McArdle equation having no age term at all.