Wondering how to calculate BMR manually? You only need a pen, your age, height, weight and sex — the Mifflin-St Jeor formula does the rest. We walk through it step by step below with a worked example, and the free calculator above applies the same formula instantly so you can check your answer. No signup, results in seconds.
Your Basal Metabolic Rate is the energy your body needs just to stay alive — keeping your heart beating, lungs breathing and cells repairing while you lie completely still. For most people it makes up 60–70% of all calories burned in a day. Everything else — walking, working, exercising, even digesting food — sits on top of it.
How to calculate BMR manually
Nutrition professionals trust the Mifflin-St Jeor formula because it has proven the most accurate for typical adults. Grab your numbers and follow along:
Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Worked example: a 30-year-old man who weighs 75 kg and is 175 cm tall → (10 × 75) + (6.25 × 175) − (5 × 30) + 5 = 750 + 1,093.75 − 150 + 5 ≈ 1,699 calories per day at rest. Now type your own numbers into the calculator above and see if your hand calculation matches.
Muscle burns more than fat at rest, which is why two people of the same weight can have different BMRs — but for planning purposes, this equation is the gold standard.
BMR vs TDEE: which number matters?
BMR is your floor; TDEE (Total Daily Energy Expenditure) is your real life. Multiply BMR by an activity factor (1.2 for a desk job up to 1.9 for athletes) and you get the calories that maintain your current weight. Want to lose weight? Eat moderately below TDEE. Want to gain muscle? Eat slightly above it with enough protein. Never stay below your BMR for long without medical supervision — that is the energy your organs need to function.
Frequently asked questions
How to calculate BMR manually with the Mifflin-St Jeor formula?
Plug your numbers into the Mifflin-St Jeor equation. Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. Women: the same formula, but − 161 at the end. A 30-year-old man, 175 cm, 75 kg gets about 1,699 calories per day. Enter your numbers in the calculator above to check your math instantly.
Can I learn how to calculate BMR manually and check it with a free online calculator?
Yes. Work through the formula by hand using the steps above, then enter the same numbers in the free calculator to verify your answer — no signup needed.
What is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to keep you alive — breathing, circulation, cell repair. It typically accounts for 60–70% of daily calorie burn.
How is BMR calculated?
This calculator uses the Mifflin-St Jeor equation, considered the most accurate for the general population: it combines your weight, height, age and sex into a daily calorie figure.
What is the difference between BMR and TDEE?
BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) is BMR plus everything you do — moving, working, exercising. TDEE is the number that matters for weight goals.
How many calories should I eat to lose weight?
A common guideline is eating about 500 calories below your TDEE per day for roughly 0.5 kg of fat loss per week. Never eat below your BMR for long without medical guidance.
Is this BMR calculator free?
Yes. It is 100% free with no signup required.
How can I calculate my BMR at home without equipment?
To calculate your BMR at home without equipment, use the Mifflin-St Jeor equation with just your age, height, weight and sex — no lab test needed. Enter those four numbers above and this calculator applies the formula instantly.
What is a normal BMR for my age and weight?
A normal BMR depends on your age, weight, height and sex: most adults fall between 1,200 and 2,000 calories per day at rest. Calculate your BMR at home with the tool above to see your personal number, then compare it with your total daily calorie needs.
How often should I recalculate my BMR?
Recalculate whenever your weight shifts by about 5 kg, or once a year as you age, since BMR drifts downward with both age and weight loss. If you're tracking calories toward a goal, refreshing your BMR every few months keeps your targets honest instead of silently stale.
Why is my BMR lower than my friend's at the same weight?
BMR depends on height, age, and sex as well as weight — a taller or younger person burns more at rest, and men typically run 5–10% higher than women at equal weight. Muscle mass raises it further, which the formula only approximates, so two people at 75 kg can legitimately differ by 200+ calories.
Should I eat below my BMR to lose weight faster?
No — prolonged eating below BMR risks muscle loss, fatigue, hormonal disruption, and stalled progress. Use BMR as your floor and build the deficit from TDEE instead (typically around 500 kcal under maintenance), which is aggressive enough without being destructive.
The Mifflin-St Jeor formula, worked through
BMR — basal metabolic rate — is the calories your body burns at complete rest to stay alive: breathing, circulation, brain function, cell repair. It typically accounts for 60–70% of your total daily burn, which is why every calorie target starts here. The Mifflin-St Jeor equation (1990) is the most validated formula for the general population, outperforming the older Harris-Benedict equation in studies of healthy adults.
The formulas, with W = weight in kg, H = height in cm, A = age in years: Men: BMR = 10×W + 6.25×H − 5×A + 5 Women: BMR = 10×W + 6.25×H − 5×A − 161 Weight dominates the result, height adds a smaller share, and each year of age subtracts 5 calories — the slow metabolic decline of aging, quantified.
Worked example — a 30-year-old man, 75 kg, 175 cm: 10×75 = 750; 6.25×175 = 1093.75; 5×30 = 150. BMR = 750 + 1093.75 − 150 + 5 = 1698.75 ≈ 1,699 kcal/day. The same woman: 750 + 1093.75 − 150 − 161 = 1532.75 ≈ 1,533 kcal/day. Multiply by an activity factor (1.2 sedentary → 1.9 very active) to get TDEE, the number that actually governs weight change.
Practical tips: BMR is your metabolic floor, not your calorie target — eating targets come from TDEE. Recalculate after every ~5 kg of weight change. Limitation: the formula assumes average body composition, so it underestimates very muscular people and overestimates very high body-fat percentages; the Katch-McArdle equation (which uses body-fat %) is more accurate if you know that number.
From BMR to daily calories — the activity multipliers: BMR alone doesn't tell you what to eat; multiply it by an activity factor to get TDEE. The standard Harris-Benedict multipliers: 1.2 (sedentary, desk job, no exercise), 1.375 (light exercise 1–3 days/week), 1.55 (moderate, 3–5 days), 1.725 (hard, 6–7 days), 1.9 (very hard physical job or twice-daily training). Our 1,699-BMR example at moderate activity: 1699 × 1.55 ≈ 2,633 kcal/day maintenance. A 500 kcal deficit from that number — not from BMR — yields roughly 0.5 kg of fat loss per week. One caution: prolonged aggressive dieting triggers adaptive thermogenesis, where the body burns 5–15% less than formulas predict; if weight loss stalls for 3+ weeks despite accurate tracking, recalculate with one activity tier lower rather than slashing food further.