Free calculator
BMR Calculator (Basal Metabolic Rate)
Written by the GymStreak coaching teamUpdated
Adds the Katch-McArdle estimate, which uses lean mass.
The short answer
Your basal metabolic rate (BMR) is the number of calories your body would burn in a day at complete rest, just to keep you alive. The most reliable everyday formula is Mifflin-St Jeor: for men, BMR = 10 × weight in kg + 6.25 × height in cm − 5 × age + 5 (for women, subtract 161 instead of adding 5). A 30-year-old man who is 180 cm and 80 kg has a BMR of about 1,780 calories.
01 / How it works
How the bmr calculator works
Even lying still, your body spends energy on breathing, pumping blood, keeping warm and running your organs. That baseline is your basal metabolic rate, and for most people it is the biggest single part of the calories they burn in a day. Measuring it takes a lab and a breathing mask, so the calculator estimates it from your sex, age, height and weight.
The headline number uses the Mifflin-St Jeor equation, published in 1990 from measurements of 498 men and women aged 19 to 78. Reviews comparing the common equations with measured resting burn found it was the most reliable of them. The calculator also shows the revised Harris-Benedict equation, an older formula many sites still use, which usually reads a little higher. If you know your body fat percentage, it adds the Katch-McArdle estimate, which works from lean mass instead of total weight.
Strictly, these equations predict resting metabolic rate (RMR), measured awake and at rest, rather than a true basal rate taken after a night's sleep in a lab. The two are close, and most people use the terms interchangeably. Below your result, the calculator multiplies your BMR by the usual activity factors to show roughly how many calories you burn once exercise and daily movement are added.
02 / Formula
The BMR formulas
Mifflin-St Jeor equation (used for the main result)
Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5 Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
- weight in kilograms (pounds × 0.4536)
- height in centimetres (inches × 2.54)
- age in years
- BMR in kilocalories (calories) per day
Harris-Benedict equation, revised (shown alongside)
Men: BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age Women: BMR = 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age
- same units as above
The original Harris-Benedict equations date from 1919. Roza and Shizgal re-fitted them in 1984 on a larger data set and reported a precision of about ±14% in healthy adults.
Katch-McArdle (Cunningham) equation (if you enter body fat)
BMR = 370 + 21.6 × lean body mass Lean body mass = weight × (1 − body fat % ÷ 100)
- weight and lean body mass in kilograms
Because it ignores fat mass, this version can suit lean, muscular people better than weight-based equations, but it is only as good as your body fat estimate. Try the body fat calculator if you do not know yours.
Calories burned with exercise
Daily calories ≈ BMR × activity factor
- activity factor = 1.2 (sedentary) to 1.9 (very active)
The activity factors are conventional estimates used by dietitians and coaches rather than values from a single study. See the table below, or use the TDEE calculator for a full calorie target.
03 / Worked example
Worked examples
A 30-year-old man, 180 cm and 80 kg
He enters his details in metric. He also knows from a tape estimate that he is about 18% body fat.
- 1Mifflin-St Jeor = 10 × 80 + 6.25 × 180 − 5 × 30 + 5
- 2= 800 + 1,125 − 150 + 5 = 1,780 kcal
- 3Harris-Benedict = 88.362 + 13.397 × 80 + 4.799 × 180 − 5.677 × 30
- 4= 88.4 + 1,071.8 + 863.8 − 170.3 ≈ 1,854 kcal
- 5Lean mass = 80 × (1 − 0.18) = 65.6 kg
- 6Katch-McArdle = 370 + 21.6 × 65.6 ≈ 1,787 kcal
His BMR is about 1,780 calories a day. The three equations land within about 75 calories of each other, which is typical for someone of average build.
A 35-year-old woman, 165 cm and 65 kg
She enters her details in metric.
- 1Mifflin-St Jeor = 10 × 65 + 6.25 × 165 − 5 × 35 − 161
- 2= 650 + 1,031.25 − 175 − 161 ≈ 1,345 kcal
- 3Harris-Benedict = 447.593 + 9.247 × 65 + 3.098 × 165 − 4.330 × 35
- 4= 447.6 + 601.1 + 511.2 − 151.6 ≈ 1,408 kcal
Her BMR is about 1,345 calories a day. Harris-Benedict reads about 60 calories higher.
In pounds and feet: a 40-year-old woman, 5 ft 5 in and 150 lb
The calculator converts imperial inputs to metric first.
- 1Weight = 150 × 0.4536 = 68.0 kg
- 2Height = 65 in × 2.54 = 165.1 cm
- 3BMR = 10 × 68.0 + 6.25 × 165.1 − 5 × 40 − 161
- 4= 680.4 + 1,031.9 − 200 − 161 ≈ 1,351 kcal
Her BMR is about 1,351 calories a day.
04 / Reference
BMR charts and tables
| Age | 60 kg (132 lb) | 70 kg (154 lb) | 80 kg (176 lb) | 90 kg (198 lb) | 100 kg (220 lb) |
|---|---|---|---|---|---|
| 25 | 1,593 | 1,693 | 1,793 | 1,893 | 1,993 |
| 35 | 1,543 | 1,643 | 1,743 | 1,843 | 1,943 |
| 45 | 1,493 | 1,593 | 1,693 | 1,793 | 1,893 |
| 55 | 1,443 | 1,543 | 1,643 | 1,743 | 1,843 |
| 65 | 1,393 | 1,493 | 1,593 | 1,693 | 1,793 |
Every 10 kg adds 100 calories and every 10 years takes away 50, because the equation is a straight line in each input.
| Age | 50 kg (110 lb) | 60 kg (132 lb) | 70 kg (154 lb) | 80 kg (176 lb) | 90 kg (198 lb) |
|---|---|---|---|---|---|
| 25 | 1,245 | 1,345 | 1,445 | 1,545 | 1,645 |
| 35 | 1,195 | 1,295 | 1,395 | 1,495 | 1,595 |
| 45 | 1,145 | 1,245 | 1,345 | 1,445 | 1,545 |
| 55 | 1,095 | 1,195 | 1,295 | 1,395 | 1,495 |
| 65 | 1,045 | 1,145 | 1,245 | 1,345 | 1,445 |
| Activity level | Typical week | Factor | For a BMR of 1,780 |
|---|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 | 2,136 kcal |
| Light | Exercise 1–3 days a week | 1.375 | 2,448 kcal |
| Moderate | Exercise 3–5 days a week | 1.55 | 2,759 kcal |
| Active | Hard exercise 6–7 days a week | 1.725 | 3,071 kcal |
| Very active | Hard daily training plus a physical job | 1.9 | 3,382 kcal |
Conventional estimates, not measurements. Pick the level that matches a normal week, and treat the result as a starting point to check against your scale.
05 / Training
How to use your BMR
- Do not eat your BMR to lose weight. It is what you burn lying still, not your daily need. Multiply it by an activity factor (or use the TDEE calculator) to get your maintenance calories, then eat a little below that.
- Turn it into macros. The macro calculator uses the same Mifflin-St Jeor BMR and splits your target into protein, fat and carbs.
- Build muscle to nudge it up, a little. Muscle burns more at rest than fat, but the difference per kilogram is modest. Does building muscle increase metabolism? puts a number on it. Squats, deadlifts and rows such as barbell squats, the barbell deadlift and bent over rows train the most muscle at once.
- Move more outside the gym. Walking and everyday movement change your total burn far more than your BMR does. Read the easy way to boost your metabolism: NEAT.
- Recalculate as your weight changes. A lighter body burns less at rest, which is one reason weight loss slows. See can weight loss "damage" your metabolism?.
06 / Limitations
Limitations and safety
Every equation predicts the average for people like you, not your own metabolism. In a 2013 study of 337 adults, Mifflin-St Jeor came within 10% of measured resting burn for 82% of people: 87% of those without obesity but only 75% of those with obesity. The other common equations, including Harris-Benedict, tended to overestimate.
Older adults and ethnic minority groups were under-represented in the studies used to build and test these equations, so estimates for them are less certain. The equations are for adults and are not designed for children, pregnancy or illness.
Resting burn depends mostly on lean mass, so equations based on total weight can underestimate people who carry a lot of muscle. If that is you, the Katch-McArdle figure may be closer, provided your body fat estimate is reasonable.
This calculator gives an estimate for general fitness education. It is not medical advice and does not diagnose anything. If you have a health condition, are pregnant, or are new to hard exercise, check with a doctor first.
07 / FAQ
Frequently asked questions
What is basal metabolic rate?
Basal metabolic rate (BMR) is the energy your body uses in a day at complete rest to keep you alive: breathing, circulation, temperature control and organ function. It is usually given in calories (kilocalories) per day.
How do I calculate my BMR?
Use the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age in years, then add 5 for men or subtract 161 for women. For example, a 35-year-old woman who is 165 cm and 65 kg has a BMR of about 1,345 calories a day.
Which BMR formula is most accurate?
For healthy adults, Mifflin-St Jeor is the best-supported of the common equations. A systematic review found it predicted resting burn within 10% for more people than any other equation it tested, and it had the narrowest error range. Harris-Benedict tends to read a little higher.
How do I calculate BMR with exercise?
Multiply your BMR by an activity factor: 1.2 if you are mostly sedentary, 1.375 for exercise 1 to 3 days a week, 1.55 for 3 to 5 days, 1.725 for hard exercise 6 to 7 days and 1.9 for very hard daily training plus a physical job. With a BMR of 1,780 and moderate activity, that is about 2,760 calories a day.
What is the difference between BMR and RMR?
BMR is measured in strict lab conditions, lying down after a night's sleep and an overnight fast. Resting metabolic rate (RMR) is measured awake and at rest under looser conditions and usually comes out a little higher. The equations on this page predict resting burn, and most people treat the two terms as the same.
Should I eat my BMR to lose weight?
No. Your BMR does not include the calories you burn moving, exercising and digesting food, so eating only your BMR is usually a large deficit. For steady fat loss, most people start about 500 calories below their total daily burn (TDEE) instead.
Why does my BMR go down as I get older?
In the Mifflin-St Jeor equation, each extra year of age lowers BMR by 5 calories a day, so ten years takes away about 50. That is an average across the people studied; your own change depends partly on how much muscle you keep, and strength training is the part you control.
Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182.
- Cunningham JJ. Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. Am J Clin Nutr. 1991;54(6):963-969.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789.
- Frankenfield DC. Bias and accuracy of resting metabolic rate equations in non-obese and obese adults. Clin Nutr. 2013;32(6):976-982.
Related tools
- TDEE CalculatorEstimate the calories you burn per day, then get a target for losing, keeping or gaining weight.
- Macro CalculatorGet daily calories and grams of protein, fat and carbs for losing fat, maintaining or building muscle.
- Body Fat CalculatorEstimate your body fat percentage with a tape measure, using the US Navy method in cm or inches.
From the blog
Exercises to try
- Barbell SquatsBeginner compound barbell exercise for the quadriceps, also working the glutes.
- Barbell DeadliftIntermediate compound barbell exercise for the hamstrings, also working the glutes, abs and calves.
- Bent Over RowsBeginner compound barbell exercise for the middle back, also working the lats, shoulders and lower back.
- TreadmillBeginner cardio on the treadmill, for heart and lung fitness.
Know your number, then hit it
GymStreak lets you log meals from a photo or a quick typed or spoken description, and syncs energy and nutrition with Apple Health or Health Connect.
