BMR Calculator: Find Your Basal and Resting Metabolic Rate
Basal metabolic rate (BMR) is the calories your body burns at complete rest, just to keep you alive; resting metabolic rate (RMR) is the same idea measured under slightly looser conditions. For a 30-year-old woman of 65 kg and 165 cm it is about 1,370 kcal a day; for a 28-year-old man of 75 kg and 178 cm, about 1,728 kcal. Enter your details for your own number. The guide below uses the same Mifflin-St Jeor result as the form.
Enter Your Details
BMR is the minimum energy your body needs to sustain life while completely at rest.
BMR Calculator
Estimate your resting daily energy baseline
The energy your body needs for basic survival functions — breathing, circulation, cell production — while completely at rest.
Sedentary
Little or no exercise
Lightly Active
Light exercise 1-3 days/week
Moderately Active
Moderate exercise 3-5 days/week
Very Active
Heavy exercise 6-7 days/week
Extremely Active
Athletic training or physical job
What Is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs to carry out its most basic, life-sustaining functions while at complete rest: breathing, circulating blood, cell repair, and regulating body temperature. It does not include digestion, movement, or exercise — that additional energy is what turns BMR into your full TDEE.
Organ Function
Per kilogram, the heart and kidneys burn about 440 kcal a day at rest, the brain 240 and the liver 200, against 13 for muscle and 4.5 for fat (Wang et al., 2010).
Temperature Regulation
Maintaining core body temperature at ~37°C requires constant, measurable energy expenditure.
Cellular Maintenance
Cell turnover, hormone production, and protein synthesis all draw from your basal energy pool.
The Mifflin-St Jeor Equation
A 2005 review for the American Dietetic Association found it more likely than other equations tested to estimate resting metabolic rate within 10% of measured values.
BMR = (10 × weight [kg]) + (6.25 × height [cm]) - (5 × age [years]) + 5
BMR = (10 × weight [kg]) + (6.25 × height [cm]) - (5 × age [years]) - 161
Harris-Benedict (Revised, 1984)
An older but still widely used alternative. Tends to run slightly higher than Mifflin-St Jeor for most body types.
BMR = 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
BMR = 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)
BMR vs TDEE: What's the Difference?
Eating below your BMR for weeks is a large deficit, and energy expenditure tends to fall during long diets (Rosenbaum & Leibel, 2010). Treat BMR as a floor, not a target.
Basal Metabolic Rate (BMR)
The absolute energetic floor required to sustain life in a thermo-neutral state while completely motionless. Usually about 60–70% of daily burn.
Total Daily Energy (TDEE)
Your BMR plus digestion, daily movement, and exercise. This is the real number to use for weight loss, maintenance, or gain targets.
Calculate your full TDEEHow to Calculate BMR
Basal metabolic rate (BMR) is the calories your body burns at complete rest, before walking, training or digesting food. This free BMR calculator estimates that number with the Mifflin-St Jeor equation, then shows what happens when you multiply it by an activity level. It runs in the browser. No account is required.
- Use weight, height, age and sex: Mifflin-St Jeor for men is (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women the constant is −161 instead of +5.
- Round to the nearest calorie: The result card prints that rounded BMR. The calculator will not print a figure under 500 kcal.
- Read the activity rows as TDEE, not as BMR: Each row is the rounded BMR times a multiplier: sedentary × 1.2, lightly active × 1.375, moderately active × 1.55, very active × 1.725, extremely active × 1.9. That product is total daily energy expenditure. The full TDEE calculator starts from the same idea.
- Switch formula only if you want the comparison: Revised Harris-Benedict uses a different equation. It does not change your weight, height or age.
Worked example with the form defaults
The form opens on a 28-year-old man, 75 kg, 178 cm, and Mifflin-St Jeor. BMR is (10 × 75) + (6.25 × 178) − (5 × 28) + 5 = 1,727.5 kcal, which this page rounds to 1,728 kcal.
The activity rows on that 1,728 kcal BMR are sedentary 2,074, lightly active 2,376, moderately active 2,678, very active 2,981, and extremely active 3,283 kcal. To get TDEE from BMR, multiply the rounded BMR by the row you actually live, not by the highest row.
Mifflin-St Jeor and revised Harris-Benedict
Leave the formula on Mifflin-St Jeor unless you are comparing. Revised Harris-Benedict for men is 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age). On the opening inputs that is 1,788.4 kcal, which prints as 1,788 kcal, 60 kcal above Mifflin.
A 2005 review found Mifflin-St Jeor more likely than the other equations it tested to land within 10% of measured resting metabolism. That is why this form opens on Mifflin. It is not a claim that every person will match a lab measurement. The formula comparison includes the other equations, including ones that start from body fat. This form does not ask for a body-fat percentage. Muscle does raise resting burn, and a weight-only equation can only approximate that. The body fat calculator is the separate estimate.
BMR calculator for women
Choose Female. Only the constant changes. A 30-year-old woman, 65 kg, 165 cm: (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 1,370.25 kcal, which rounds to 1,370 kcal. Revised Harris-Benedict for women is 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age). On these inputs that prints as 1,430 kcal.
Her activity rows, from the rounded Mifflin BMR of 1,370, are sedentary 1,644, lightly active 1,884, moderately active 2,124, very active 2,363, and extremely active 2,603 kcal. Men and women with the same height, weight and age do not get the same BMR, because the constant differs.
BMR and weight loss
BMR is not a weight-loss target. Eating at 1,728 kcal would mean the opening example is eating his resting burn and nothing for movement. Weight loss starts from TDEE. His moderately active row is 2,678 kcal. The calorie calculator subtracts 250, 500 or 750 kcal from that TDEE. Moderate is 2,178 kcal, which stays above his BMR of 1,728. If a deficit would fall under BMR, that calorie page holds the target at BMR instead.
RMR calculator: BMR vs resting metabolic rate
Resting metabolic rate (RMR), also called resting energy expenditure, is measured lying still but with fewer restrictions than BMR, which needs an overnight fast, a full night's sleep and a strictly controlled room. RMR usually reads a little higher. For everyday planning the two are close enough to use interchangeably.
The Mifflin-St Jeor equation this page uses was built from resting energy expenditure measured by indirect calorimetry in 498 adults (Mifflin et al., 1990), so the number it prints is really an RMR estimate, even though calculators label it BMR. To find your resting metabolic rate here, enter your details with Mifflin-St Jeor selected: the opening man gets 1,728 kcal a day and the opening woman 1,370. Only a lab or clinic test with indirect calorimetry measures RMR directly; a bathroom scale or watch estimates it.
The age field starts at 14. Mifflin-St Jeor and revised Harris-Benedict are adult equations. A teenager who is still growing should not turn this result into a calorie cut. That target belongs with a clinician.
BMR by age
Mifflin-St Jeor takes 5 kcal off for each year of age, so it drops about 50 kcal a decade if nothing else changes. This chart holds height and weight steady to show only the age effect:
| Age | Woman, 65 kg, 165 cm | Man, 75 kg, 178 cm |
|---|---|---|
| 20 | 1,420 kcal | 1,768 kcal |
| 30 | 1,370 kcal | 1,718 kcal |
| 40 | 1,320 kcal | 1,668 kcal |
| 50 | 1,270 kcal | 1,618 kcal |
| 60 | 1,220 kcal | 1,568 kcal |
| 70 | 1,170 kcal | 1,518 kcal |
These are equation outputs, not population averages. Real changes with age come mostly from losing lean mass. A study of daily energy expenditure measured in thousands of people from 8 days to 95 years old found that, once fat-free mass was accounted for, expenditure stayed stable from about 20 to 60 and declined only after that (Pontzer et al., 2021).
What affects your BMR?
Body size and composition do most of the work. In a study of 150 adults in Scotland, fat-free mass explained 63% of the differences in BMR between people, fat mass 6% and age 2%, while 26% stayed unexplained (Johnstone et al., 2005). Organs are the most expensive tissue to run:
| Tissue | kcal per kg per day at rest |
|---|---|
| Heart and kidneys | 440 |
| Brain | 240 |
| Liver | 200 |
| Skeletal muscle | 13 |
| Fat (adipose tissue) | 4.5 |
Values from Elia, confirmed in adults by MRI and calorimetry (Wang et al., 2010). They were about 3% lower in adults over 50.
How to increase your BMR
The lasting way is to carry more lean mass, mainly through resistance training with enough protein. Expect a small change: at about 13 kcal per kilogram of muscle a day, gaining 2 kg of muscle adds roughly 26 kcal to resting burn. Training also burns energy directly, which usually matters more than the BMR change. Eating well below your needs for a long time works the other way, because expenditure tends to fall.
Low or high BMR: what it means
A BMR that looks low is usually a smaller body, or more fat mass relative to lean mass, not a broken metabolism. Thyroid hormone also plays a part: in the Scottish study, thyroxine explained a quarter of the otherwise unexplained variation in men (Johnstone et al., 2005). If you have symptoms such as constant tiredness, feeling cold or unexplained weight change, ask your doctor about a thyroid test rather than adjusting calories on your own.
A bathroom scale that shows BMR does not measure it. It estimates BMR from your weight, the details you enter and its own body-fat reading, so it can differ from this calculator. Measuring BMR needs indirect calorimetry in a clinic or lab.
Frequently Asked Questions
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. American Journal of Clinical Nutrition. 1990;51(2):241–247.
- Harris JA, Benedict FG. A biometric study of human basal metabolism. Proceedings of the National Academy of Sciences. 1918;4(12):370–373.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition. 1984;40(1):168–182.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775–789.
- Wang Z, Ying Z, Bosy-Westphal A, et al. Specific metabolic rates of major organs and tissues across adulthood: evaluation by mechanistic model of resting energy expenditure. American Journal of Clinical Nutrition. 2010;92(6):1369–1377.
- Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808–812.
- Johnstone AM, Murison SD, Duncan JS, Rance KA, Speakman JR. Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine. American Journal of Clinical Nutrition. 2005;82(5):941–948.
- Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. International Journal of Obesity. 2010;34(Suppl 1):S47–S55.
Results are estimates for healthy adults, not medical advice. See the medical disclaimer and how these calculators work.