BMR Calculator — Basal Metabolic Rate
Calculate your Basal Metabolic Rate (BMR) with Mifflin-St Jeor and Harris-Benedict equations. See resting calories and BMR vs TDEE.
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CalcVita. (2026). BMR Calculator — Basal Metabolic Rate. CalcVita. Retrieved October 17, 2026, from https://calcvita.com/en/calculators/bmr
How It Works
Enter your biological sex, age, weight, and height. The calculator applies two validated equations — Mifflin-St Jeor (1990) and revised Harris-Benedict (1984) — and returns your Basal Metabolic Rate in kcal/day. BMR is the number of calories your body burns per day doing nothing but sustaining life.
Mifflin-St Jeor Equation (Recommended)
Men: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5. Women: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161. Published in 1990, and identified by a 2005 systematic review as the equation most likely to land within ±10% of measured BMR (Frankenfield 2005, PMID 15883556).
Revised Harris-Benedict Equation
Men: 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age). Women: 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age). Originally published in 1919 and revised by Roza & Shizgal in 1984 (PMID 6741850). In Mifflin’s 1990 sample, the original equations overestimated measured BMR by 5%.
From BMR to TDEE
Multiply your BMR by an activity factor to get TDEE: 1.2 (sedentary, little/no exercise), 1.375 (lightly active, 1–3 days/week), 1.55 (moderately active, 3–5 days/week), 1.725 (very active, 6–7 days/week), 1.9 (extremely active, physical job + daily training). TDEE is your maintenance calorie level.
Practical Tips
Use Mifflin-St Jeor as your primary BMR estimate. It is the most validated formula for general adult populations. Compare with Harris-Benedict to understand your possible range.
BMR is a resting value — never use it as your eating target. Always calculate TDEE (BMR × activity factor) before setting a calorie goal.
BMR equations assume average body composition. Athletes with high muscle mass may have a higher BMR than predicted. Track real weight changes over 2–4 weeks to calibrate your actual TDEE.
Scientific Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7. PMID 2305711
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr. 1984;40(1):168–82. PMID 6741850
- Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA. 1918;4(12):370–3.
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate in healthy non-obese and obese adults. J Am Diet Assoc. 2005;105(5):775–89. PMID 15883556
- What is BMR (Basal Metabolic Rate)?
- BMR is the number of calories your body needs to maintain basic physiological functions — breathing, circulation, cell production, and temperature regulation — while completely at rest. It represents your minimum calorie requirement and typically accounts for 60–75% of total daily energy expenditure.
- What is the difference between BMR and TDEE?
- BMR is the calories burned at complete rest. TDEE (Total Daily Energy Expenditure) adds the calories burned through physical activity, digestion (thermic effect of food), and non-exercise movements. TDEE = BMR × activity multiplier (1.2 for sedentary up to 1.9 for very active). BMR is always lower than TDEE.
- Which formula is more accurate — Mifflin-St Jeor or Harris-Benedict?
- The Mifflin-St Jeor equation (1990) is generally considered more accurate for modern populations. A 2005 systematic review (Frankenfield et al.) found that it estimated resting metabolic rate within 10% of the measured value in more non-obese and obese adults than any other equation. In Mifflin’s own 1990 sample, the original Harris-Benedict equations overestimated measured values by 5%. Both are marked as estimates and should be combined with real-world energy tracking.
- How can I use my BMR to lose or gain weight?
- First calculate your TDEE (BMR × activity factor). To lose weight, eat below your TDEE — a deficit of 500 kcal/day produces roughly 0.45 kg/week. To gain muscle, eat slightly above TDEE (200–300 kcal surplus). Never eat below your BMR for extended periods, as this risks muscle wasting and metabolic slowdown.
- Does BMR change with age?
- Yes. BMR decreases with age, primarily due to a reduction in lean muscle mass (sarcopenia). In a large 2021 study using doubly labelled water (Pontzer et al., Science), energy expenditure adjusted for lean mass stayed stable between ages 20 and 60 and declined after 60. Regular resistance training can significantly slow this decline by preserving muscle tissue.
Suggested article
BMR vs TDEE: What's the Difference and Why It Matters
BMR and TDEE are not the same. Understanding the difference—and how your activity level bridges the gap—is the foundation of any successful weight management plan.
Read the full article →More calculators
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