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Health & Body
BMR Calculator — Basal Metabolic Rate (Mifflin-St Jeor)
The calories you'd burn lying in bed all day — your metabolic baseline
Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to keep you alive at complete rest — breathing, pumping blood, keeping your brain and organs running, holding your body temperature steady. It's the energy you'd use lying still in bed all day, eating nothing and moving nothing. For most adults, BMR is the largest single piece of daily calorie burn, usually 60–70% of the total, which is why it's the starting point for any weight-loss, maintenance, or muscle-gain plan.
This calculator uses the Mifflin-St Jeor equation, the formula registered dietitians and the Academy of Nutrition and Dietetics consider the most accurate for the general population. It runs on metric internally, so we convert your American units first: pounds to kilograms (lb ÷ 2.205) and feet-plus-inches to centimeters (total inches × 2.54).
The formula:
- Men: BMR = 10 × kg + 6.25 × cm − 5 × age + 5
- Women: BMR = 10 × kg + 6.25 × cm − 5 × age − 161
Worked example. A 30-year-old man, 5 ft 10 in, 160 lb. Convert: 160 lb = 72.6 kg; 5 ft 10 in = 70 in = 177.8 cm. Then BMR = 10 × 72.6 + 6.25 × 177.8 − 5 × 30 + 5 = 726 + 1,111 − 150 + 5 = about 1,692 calories per day.
The single biggest mistake people make is confusing BMR with TDEE. BMR is your burn at rest — you almost never eat at that level. Your real daily need is your Total Daily Energy Expenditure (TDEE), which is BMR multiplied by an activity factor (1.2 for sedentary up to 1.9 for very heavy training). Eating right at your BMR while you're walking, working and exercising means a steep, often unintended calorie deficit. So this tool shows you both: your BMR and a quick table of TDEE estimates at each activity level.
A second trap: leaving your height as 5.10 instead of converting to 70 total inches. Always do feet × 12 + inches first — this calculator handles that step when you enter feet and inches separately.
Treat this as a metabolic ballpark for planning, not medical or nutrition advice. Two people with identical stats can have BMRs that differ by 100+ calories because the equation can't see body composition, genetics, thyroid function or other health conditions. Use the number to set a starting calorie target, then verify it against your real-world results and a doctor or registered dietitian before making big diet changes.
Calculator
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📰 Formula
• Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 • Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161 • Convert: kg = lb ÷ 2.2046 · cm = (feet × 12 + inches) × 2.54 • TDEE = BMR × activity factor (1.2 sedentary → 1.9 very active) • BMR ≠ TDEE: BMR is rest only; TDEE is your real daily need
📰 Formula
• Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 • Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161 • Convert: kg = lb ÷ 2.2046 · cm = (feet × 12 + inches) × 2.54 • TDEE = BMR × activity factor (1.2 sedentary → 1.9 very active) • BMR ≠ TDEE: BMR is rest only; TDEE is your real daily need
🧪 Worked examples
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⚠️ Common mistakes
- Confusing BMR (calories at rest) with TDEE (your actual daily need with activity).
- Eating exactly at BMR while active, creating a much larger deficit than intended.
- Entering height as a decimal (5.10) instead of total inches (70).
- Using the wrong sex constant — men add 5, women subtract 161.
💡 Tips
- Multiply BMR by your activity factor to get TDEE — never eat at BMR alone.
- Convert height to inches first: feet × 12 + inches, then on to centimeters.
- Re-run it after big weight changes; BMR drops as you lose weight.
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❓ Frequently asked questions
What is BMR and what does it measure?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest in a day — just to run your organs, breathing and temperature. It excludes any movement, digestion or exercise.
What's the difference between BMR and TDEE?
BMR is your burn at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor (1.2 to 1.9) and reflects what you actually burn day to day. TDEE is the number to base your calorie goal on.
How do I calculate BMR with pounds and feet?
Convert first: pounds ÷ 2.2046 = kg, and (feet × 12 + inches) × 2.54 = cm. Then use Mifflin-St Jeor: men 10×kg + 6.25×cm − 5×age + 5; women the same but − 161.
Which BMR formula is most accurate?
Mifflin-St Jeor is considered the most accurate for the general population by the Academy of Nutrition and Dietetics. Older formulas like Harris-Benedict tend to read a bit high.
How many calories should I eat to lose weight?
Start from your TDEE (not BMR) and subtract about 500 calories per day for roughly 1 lb of loss per week. Don't drop below your BMR without medical guidance.
Is it safe to eat below my BMR?
Generally no. Eating below your resting burn for long stretches can cost you muscle and energy. Aim for a moderate deficit from TDEE, and talk to a doctor or dietitian before going very low.
Why is my BMR different from someone the same weight?
BMR depends on sex, age and height too, not just weight. Men burn more at rest (the +5 vs −161 constant), younger people burn more, and taller people burn more, even at equal weight.
Does muscle change my BMR?
Yes — muscle is more metabolically active than fat, so more lean mass raises BMR. The Mifflin-St Jeor formula uses only weight and doesn't see body composition, so very muscular people may run higher than the estimate.
How often should I recalculate my BMR?
Recalculate after a meaningful weight change (5–10 lb) or every few months. BMR falls as you lose weight, so an old number will overstate your needs over time.