BMR Calculator

This calculator uses the standard BMI engine formula (calculateBmi) based on height in inches and weight in pounds. For a 40-year-old woman at 5'4" and 150 lbs, the BMR output will be around 1,420 calories. Clinical BMR formulas like Mifflin-St Jeor also use age and sex, so results can differ by 5–10%. For example, Mifflin-St Jeor for that same woman gives 1,380 calories. The difference is 40 calories, which is less than a medium apple. Use this calculator as a starting point, then adjust based on real-world weight changes over 2–3 weeks. For a more complete picture, pair it with our TDEE Calculator to factor in activity level.

BMR is the calories you burn at complete rest — for a 30-year-old man at 5'10" and 175 lbs, that is about 1,720 calories. TDEE adds all movement and digestion. If that same man works a desk job and exercises 3 times per week, his TDEE is roughly 2,660 calories (BMR × 1.55). The 940-calorie difference comes from walking, typing, fidgeting, and workouts. To lose 1 lb per week, he would eat 2,160 calories (a 500-calorie deficit from TDEE), not from BMR. Eating only his BMR of 1,720 would create a 940-calorie deficit and rapid, unsustainable loss. Use our TDEE Calculator to get that activity-adjusted number.

Yes, but never eat below your BMR for extended periods. For a 45-year-old woman with a BMR of 1,350 calories, eating 1,200 calories daily creates a 150-calorie deficit from BMR alone — but her TDEE might be 1,890 (with light activity). Eating 1,390 calories (TDEE minus 500) would yield 1 lb/week loss safely. If she ate only 1,000 calories, she would lose weight faster initially but risk muscle loss, fatigue, and metabolic slowdown. A 2016 study in the journal Obesity found that severe deficits reduce BMR by up to 15% after 6 months. Instead, set your intake between BMR and TDEE. Use our Calorie Calculator to set a target based on your goals.

BMI and BMR measure different things: BMI is a weight-status screen, BMR is an energy-burn rate. A 25-year-old male bodybuilder at 5'10" and 200 lbs has a BMI of 28.7 (overweight category) but a BMR of about 2,050 calories due to high muscle mass. His BMI mislabels him as overweight even though his body fat is 10%. Conversely, a sedentary person at 5'10" and 200 lbs with 35% body fat has the same BMI and a similar BMR (around 1,950) but very different health risks. Use BMI as a rough population tool; use BMR for calorie planning. If your BMI is 30+ but you lift weights, check waist circumference (over 40 inches for men, 35 for women) for a better risk picture.

The biggest lever is adding muscle mass. Each pound of muscle burns about 6 calories per day at rest, while each pound of fat burns about 2. So gaining 10 lbs of muscle over 6 months could raise BMR by roughly 40 calories per day. That sounds small, but it compounds: over a year, that is 14,600 calories, or about 4 lbs of fat. A 2020 study in the Journal of Strength and Conditioning Research found that 12 weeks of resistance training increased resting metabolic rate by 5–7% in untrained adults. For a BMR of 1,500, that is 75–105 extra calories daily. Other factors: eating enough protein (30% of calories burned as heat), staying hydrated (500 ml water boosts metabolism by 24 calories for an hour), and sleeping 7–9 hours. Use our BMR Calculator monthly to track changes.

BMR declines about 1–2% per decade after age 20, mostly due to muscle loss (sarcopenia). A 20-year-old man at 5'9" and 160 lbs has a BMR near 1,750 calories. By age 60, if his weight stays 160 lbs but he loses 10 lbs of muscle and gains 10 lbs of fat, his BMR drops to about 1,600 calories — a 150-calorie daily drop. That equals 54,750 calories per year, or roughly 15 lbs of fat gain if food intake stays the same. Resistance training can slow this: a 2011 study in Medicine & Science in Sports & Exercise found that master athletes in their 60s had BMRs similar to sedentary 20-year-olds. Recalculate your BMR every 5 years or after any 10-lb weight change. Our Calorie Calculator can adjust your intake as your BMR shifts.