BMR Calculator
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How to use
- 1 Choose units: metric (cm, kg) or US (feet/inches, pounds).
- 2 Enter your sex (biological), age in years, height, and current weight.
- 3 Click Calculate to see your BMR (calories burned at complete rest).
- 4 Review the TDEE table for five activity levels — sedentary, lightly active, moderately active, very active, and extra active.
- 5 For weight loss, eat 250–500 calories below TDEE for 0.5–1 lb per week. For weight gain, add 250–500 above TDEE.
About BMR Calculator
FAQ
Q How many calories do I burn at rest if I'm a 30-year-old woman, 5'5", 140 lb?
Using the Mifflin-St Jeor equation, that profile (158.8 kg→ 63.5 kg, 165 cm, age 30, female) gives a BMR of about 1,376 kcal/day. With a sedentary lifestyle (multiplier 1.2), TDEE is roughly 1,651 kcal/day — the calories needed to maintain current weight.
Q Is BMR the same as RMR?
They are close but not identical. BMR is measured in a strict fasted, fully rested state; Resting Metabolic Rate (RMR) is measured under less strict conditions and runs about 10% higher. The Mifflin-St Jeor equation predicts BMR; in practice the two terms are often used interchangeably in fitness apps.
Q How accurate is the Mifflin-St Jeor formula?
The Mifflin-St Jeor equation predicts BMR within ±10% of measured values for the largest share of adults compared to other formulas, according to the Academy of Nutrition and Dietetics evidence review. Individual variance can still be 200+ kcal/day due to body composition, genetics, thyroid function, and metabolic adaptation.
Q Why does my TDEE feel too high?
Most adults underestimate sedentary time and overestimate exercise. If you sit at a desk all day and do 30 minutes of light activity 3 days a week, you are likely "lightly active" (1.375) — not "moderately active" (1.55). Pick the level that matches your average week, not your best week.
Q How many calories should I eat to lose 1 pound a week?
A 3,500-calorie deficit roughly equals one pound of fat. Eating 500 calories per day below TDEE produces about 1 lb/week of weight loss. The CDC recommends not going below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision.
Q Does muscle really burn more calories than fat?
Yes, but less than gym myths suggest. A pound of muscle burns roughly 6 kcal/day at rest, vs. 2 kcal for a pound of fat. Adding 5 lb of muscle increases BMR by only 20–30 kcal/day — meaningful over years, not days.
Q Why does my BMR drop when I diet?
Adaptive thermogenesis — your body downregulates BMR by 10–15% during prolonged caloric restriction to preserve energy. This effect can persist after the diet ends, which is one reason maintaining weight loss is harder than achieving it. Strength training and adequate protein intake reduce the drop.
Q Should I eat back the calories burned during exercise?
If you've already chosen an activity-multiplied TDEE that includes typical exercise, no — adding exercise calories on top would double-count. If you used a sedentary TDEE and want to log workouts separately (My Fitness Pal style), then add half to all of the burned calories back to your daily target.
Official resources
Academy of Nutrition and Dietetics — Energy Expenditure
Academy of Nutrition and Dietetics evidence-based practice resources on predictive BMR equations.
NIH NIDDK — Body Weight Planner
NIH/NIDDK Body Weight Planner using the Hall et al. dynamic energy balance model — companion tool to BMR estimation.
Mifflin-St Jeor Original Study (PubMed)
PubMed entry for the original 1990 Mifflin et al. study validating the equation against indirect calorimetry.
NIH NHLBI — Aim for a Healthy Weight
National Heart, Lung, and Blood Institute guidance on calorie targets for weight loss and maintenance.