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BMR Calculator

Free BMR calculator using Mifflin-St Jeor, Harris-Benedict, Katch-McArdle and Schofield formulas. Get your basal metabolic rate and TDEE for cutting, maintenance or bulking.

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cm
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Result
BMR = 1730 calories/day
Your TDEE is:
Activity LevelCalorie
Sedentary2076
Lightly Active2379
Moderately Active2682
Very Active2984
Extremely Active3287
To lose weight: eat fewer calories than you burn.
To gain weight: eat more calories than you burn.
Activity Level Multipliers
Activity LevelTDEEDescription
SedentaryBMR * 1.2Little to no exercise plus a desk job.
Lightly ActiveBMR * 1.375Light exercise 1-3 days a week.
Moderately ActiveBMR * 1.55Moderate exercise 3-5 days a week.
Very ActiveBMR * 1.725Heavy exercise 6-7 days a week.
Extremely ActiveBMR * 1.9Athletes or people doing very heavy physical labour.
Example Activities by Level
ActivityActivity Level
Sitting or lying downSedentary
WalkingLightly Active
RunningModerately Active
SwimmingModerately Active
BikingModerately Active
JoggingVery Active
Weight liftingVery Active
High-intensity interval training (HIIT)Very Active
Professional athletesExtremely Active

What is Basal Metabolic Rate (BMR)?

Your basal metabolic rate is the number of calories your body would burn in 24 hours if you stayed at complete rest in a thermally neutral environment. It powers everything that keeps you alive when you do nothing - breathing, the heartbeat, body temperature, organ function, cell renewal and brain activity. In most adults BMR represents 60 to 75 percent of total daily energy expenditure, so it is the largest single number you need to understand before manipulating calories. See also our Cut and Bulk Macro Planner and the Stablecoin Yield Comparator.

What changes your BMR

  • Age: BMR drops roughly 1 to 2 percent per decade after 20, mainly because lean mass falls.
  • Sex: at the same height and weight, men usually have a higher BMR because they carry more muscle.
  • Lean body mass: every kg of muscle burns about 13 kcal a day at rest, every kg of fat only 4 kcal.
  • Body size: bigger bodies have more cells to maintain, so taller and heavier people have higher BMR.
  • Genetics, hormones and climate: thyroid status, sleep quality and cold exposure can shift BMR by 5 to 15 percent.

What is TDEE?

Total Daily Energy Expenditure is BMR multiplied by an activity factor between 1.2 and 1.9 to account for movement, exercise and the thermic effect of food. TDEE is the practical target you eat against: stay below it to lose weight, match it to maintain, exceed it to gain. Even a slightly inaccurate TDEE is fine because you adjust based on real weight changes after two to four weeks.

BMR Calculator — Free BMR calculator using Mifflin-St Jeor, Harris-Benedict, Katch-McArdle and Schofield formulas. Get your basal metabol
BMR Calculator

BMR formulas explained

Mifflin-St Jeor

Mifflin-St Jeor (1990) is the modern default. Validated against indirect calorimetry it predicts BMR within about 10 percent for most healthy adults and is the formula recommended by the Academy of Nutrition and Dietetics.

Harris-Benedict

Harris-Benedict (1919) was the original equation and is still found in old textbooks. It tends to overestimate BMR by 5 percent on average because it was built on a small sample from a century ago.

Revised Harris-Benedict

Harris-Benedict was re-derived by Roza and Shizgal in 1984 using modern data. It is closer to Mifflin-St Jeor in practice and is a fair fallback if you do not have body fat data.

Schofield

Schofield (1985) was adopted by the WHO/FAO/UNU. It uses age- and sex-specific weight coefficients and is the formula most often used in clinical and population nutrition work.

Katch-McArdle

Katch-McArdle is the only common formula based on lean body mass rather than total weight, so it is the most accurate option for people who know their body fat percentage and who are notably leaner or more muscular than average.

Frequently Asked Questions

If you do not know your body fat percentage, use Mifflin-St Jeor: it predicts measured BMR within about 10 percent for the average healthy adult and is the equation recommended by the Academy of Nutrition and Dietetics. If you do know your body fat (via DEXA, BodPod or accurate calipers) and you are noticeably leaner or more muscular than average, Katch-McArdle is more accurate because it works from lean body mass instead of total weight. The old original Harris-Benedict equation overestimates BMR by about 5 percent on average and is best avoided. Schofield is the choice if you need a formula validated for a specific age band, especially children or seniors.

Never eat at your BMR. Your BMR is what you would burn lying in bed all day - subtract from that and you are creating an aggressive deficit on top of an already low baseline, which crashes hormones, energy and training. Eat against TDEE: subtract 300 to 500 calories from TDEE for a moderate deficit, eat at TDEE to maintain, or add 250 to 500 to bulk. Many crash diets prescribed by social media are accidentally below BMR; that is one reason they trigger binge cycles and stalled progress.

Three things commonly drive measured BMR below the predicted value. First, history of dieting: repeated aggressive deficits trigger metabolic adaptation that suppresses BMR by 5 to 15 percent below predicted, an effect documented in the Biggest Loser follow-up studies. Second, low lean mass: someone the same age, height and weight but with less muscle burns less, and equations cannot see that without body fat data. Third, sub-clinical hypothyroidism or chronically poor sleep can each shave roughly 5 percent. If your weight is stable but the calculator predicts 400 calories more than you eat, your real BMR is probably lower - feed that number, not the prediction.

BMR falls roughly 1 to 2 percent per decade after age 20, but the drop is not really about age - it is about losing muscle. A 60-year-old who lifted weights for 30 years often has a BMR similar to a 30-year-old desk worker, because lean mass is the variable that matters. This is why resistance training is the single biggest lever for preserving metabolic rate as you age. Endurance training helps health but does very little for BMR; lifting heavy or doing hard bodyweight work does.

No. Total daily intake matters; meal frequency does not. Studies that controlled total calories found six small meals and two large meals produce the same 24-hour energy expenditure, the same thermic effect of food, and the same weight change. Skipping breakfast does not lower your metabolism - it just shifts when you eat. The persistent myth comes from observational studies where breakfast skippers also smoked more and ate worse overall. Eat whenever it suits your schedule, hunger and training.

On average, BMR equations are within 10 percent of measured BMR for healthy adults of normal weight, and activity multipliers add another 10 to 15 percent of uncertainty. So a TDEE from any calculator can realistically be 300 to 500 calories off without anyone being wrong. The right approach is to use the calculator output as a starting point, eat that amount for two weeks, then adjust by 100 to 200 calories based on how your scale trend, waist measurements and energy actually move. Self-correcting beats trying to find the magic number.

Yes, BMR drops when you lose weight because there is less tissue to maintain - this is expected, not damage. A 100 kg person at maintenance might burn 1900 kcal at rest; the same person at 80 kg might burn 1700. About half of that drop is the simple mass effect and is permanent at the new weight. The other half is metabolic adaptation, which is partly reversible: a structured reverse diet (raising calories 50 to 100 per week back toward maintenance), restored sleep and a return of training intensity all help BMR recover within three to six months.

Yes, but slowly and through one main lever: build muscle. Each kg of lean mass adds roughly 13 kcal to BMR, so 5 kg of gained muscle is around 65 kcal a day extra, which compounds to about 24,000 kcal a year. Other levers exist but are smaller: prioritising 7 to 9 hours of sleep can recover 50 to 100 kcal of suppressed metabolism, avoiding extreme deficits prevents adaptive thermogenesis, caffeine and green tea push BMR up by 3 to 5 percent for a few hours, and NEAT (fidgeting, walking, standing) can add 200 to 800 daily kcal independent of BMR. Lifting weights consistently beats every supplement combined.
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