BMR & TDEE Calculator
Calculate your basal metabolic rate (BMR) and total daily energy expenditure (TDEE) using the Mifflin-St Jeor equation — the formula clinicians.
Last updated: Sources verified:
The Mifflin-St Jeor equation
Men: BMR = 10·kg + 6.25·cm − 5·age + 5 Women: BMR = 10·kg + 6.25·cm − 5·age − 161
This equation was published in AJCN in 1990 and has been the predictive equation of choice for resting metabolic rate (RMR) in clinical nutrition practice since the early 2000s.
Activity factors
| Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.20 | Desk job, no formal exercise |
| Light | 1.375 | Light exercise 1–3 days/week |
| Moderate | 1.55 | Moderate exercise 3–5 days/week |
| Active | 1.725 | Hard exercise 6–7 days/week |
| Very active | 1.90 | Physical job + daily training |
Weight goals
- Maintenance: eat at TDEE
- Loss: TDEE − 300 to 500 kcal/day (sustainable; faster loss usually backfires)
- Gain: TDEE + 200 to 300 kcal/day (slower surplus = better lean mass:fat ratio)
Recalibrate every 2–3 weeks based on actual scale + measurement trends.
Frequently asked questions
What is BMR vs TDEE?
BMR (basal metabolic rate) is the energy your body uses at rest to keep core functions running: breathing, circulation, cellular maintenance. TDEE (total daily energy expenditure) is BMR multiplied by an activity factor that accounts for movement, exercise, and the thermic effect of food. Use TDEE for weight goals; use BMR for metabolic baseline tracking. The difference between BMR and TDEE is typically 20–90% — a sedentary office worker adds about 20%, an endurance athlete adds 90%.
Is a BMR of 1500 low?
Not necessarily. For an adult woman in the 18–60 range, 1500 kcal/day is a typical BMR — the average sits around 1300–1500 kcal. For an adult man it would be on the low side; the male average is closer to 1600–1900 kcal. Drivers of a lower BMR include lower body weight, lower muscle mass, older age, and prolonged low-calorie dieting. A reading below 1000 kcal/day in an adult is the band where clinicians look for metabolic adaptation or thyroid involvement.
What does a BMR of 1800 mean?
A BMR of 1800 kcal/day is a typical resting energy use for a healthy adult man around 75–85 kg, or a tall, muscular adult woman. It means your body burns 1800 kcal even if you spent 24 hours in bed. To estimate daily calorie needs, multiply by an activity factor: 1.2 for sedentary, 1.55 for moderately active, 1.725 for hard training. So a 1800 BMR with a moderate lifestyle equals about 2790 kcal/day maintenance.
What's a normal BMR for women or men?
Most adult women fall between 1300 and 1500 kcal/day, most adult men between 1600 and 1900 kcal/day. The numbers shift with weight, height, age, and lean mass. A 30-year-old woman at 65 kg and 168 cm has a Mifflin-St Jeor BMR of about 1380 kcal; a 30-year-old man at 80 kg and 178 cm sits near 1740 kcal. Athletes with extra muscle and very tall people sit higher; petite or older adults sit lower.
How do I use BMR to lose weight?
Don't subtract calories from BMR — that's the floor, not the budget. Calculate your TDEE first by multiplying BMR by an activity factor (1.2 sedentary up to 1.9 very active), then subtract 300–500 kcal/day from TDEE. That's the safe deficit zone: it produces roughly 0.3–0.5 kg/week weight loss. A 500 kcal/day deficit is the maximum NICE and most clinical guidelines recommend for sustained loss without lean-mass damage.
BMR vs TDEE — what's the difference?
BMR is your body's minimum running cost (resting only). TDEE is BMR plus everything else you do in a day. The bridge between them is the activity multiplier: 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (active), 1.9 (very active). For weight management you almost always plan around TDEE. BMR is the diagnostic baseline — it tells you whether your resting metabolism is in the expected range for your size and age.
Mifflin-St Jeor vs Harris-Benedict — which is more accurate?
Mifflin-St Jeor. Frankenfield's 2005 systematic review (PMID 15883556) found Mifflin-St Jeor within 10% of measured RMR in 82% of nonobese and 70% of obese adults. Harris-Benedict (1919, revised 1984) ran 5–8% high on average and missed the obese subgroup more often. The Academy of Nutrition and Dietetics has recommended Mifflin-St Jeor since 2005. Use the older Harris-Benedict only if the modern formula is unavailable.
How is BMR for a teenager (15–19) different?
Higher per kg. A growing adolescent burns 10–20% more resting energy than an adult of the same weight because growth itself costs energy. A 17-year-old male at 70 kg can have a BMR of 1750–1850 kcal, compared with about 1600 for an adult man at the same weight. IOM 2005 Dietary Reference Intakes use age-specific equations for under-19s. The Mifflin-St Jeor formula here is validated for adults ≥18; for younger teenagers, use a paediatric calculator.
Does BMR change with age?
Yes — it falls roughly 1–2% per decade after age 30. The main driver is lean-mass loss, not metabolism slowing on its own. A man with the same weight at 30 and 60 will see his BMR drop by 150–200 kcal because part of that weight has shifted from muscle to fat. Strength training and adequate protein (1.2–1.6 g/kg/day) slow the decline. After 65, IOM 2005 recommends rechecking calorie needs every 1–2 years.
Can BMR be too low? Is starvation mode real?
Adaptive thermogenesis is real but smaller than fitness media suggest. After significant weight loss (>10% body weight), measured RMR sits about 5–10% below what the equation predicts (Müller 2015, Rosenbaum 2008). True 'metabolic damage' below that range is uncommon and reverses with refeeding and resistance training. If you've crash-dieted for months and your BMR estimate feels far too high relative to how you actually eat, the fix is gradual calorie restoration plus strength work, not more cutting.
How can I increase my BMR?
The lever that actually works is muscle mass: each kg of additional lean tissue raises resting energy use by 10–15 kcal/day. Resistance training 2–4 times a week plus 1.2–1.6 g/kg/day of protein produces measurable BMR gains over 6–12 months. Caffeine and cold exposure add small short-term bumps (~50 kcal/day). What doesn't work: 'metabolism-boosting' supplements, eating frequency tricks, or short bursts of cardio without strength work.
Does the calculator save my data?
No. The calculation runs entirely in your browser. We never see, log, or transmit your weight, height, age, or sex. Our anonymous analytics receives only the activity-level bucket — nothing that identifies you.
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Sources
- A new predictive equation for resting energy expenditure in healthy individuals — American Journal of Clinical Nutrition (Mifflin et al., 1990) (peer reviewed, retrieved 2026-04-26)
- Comparison of predictive equations for resting metabolic rate — Journal of the American Dietetic Association (peer reviewed, retrieved 2026-04-26)