Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — just keeping you alive: breathing, circulating blood, maintaining body temperature. It is the baseline every calorie plan starts from, whether your goal is losing weight, gaining muscle or simply maintaining.
Our free BMR calculator uses the Mifflin-St Jeor equation, the formula most dietitians and researchers consider the most accurate for healthy adults. Enter your age, gender, height and weight, pick your activity level, and you get your BMR plus your Total Daily Energy Expenditure (TDEE) — the calories you actually burn per day — along with calorie targets for weight loss and weight gain.
All calculations happen in your browser. No sign-up, no data stored, no judgment — just the numbers you need to plan.
How to use the BMR calculator
- Enter your age. Metabolism slows with age, so an accurate age improves the estimate.
- Select your gender. The formula differs for men and women due to average body composition differences.
- Add height and weight. Use centimeters and kilograms for the most accurate result.
- Choose your activity level. Be honest — most desk workers are “sedentary” or “lightly active”.
- Read your numbers. BMR, daily calorie needs (TDEE), and loss/gain targets appear instantly.
- Compare activity levels. The full table shows how many calories each lifestyle burns, motivating realistic changes.
Key features & benefits
- Mifflin-St Jeor formula. The gold-standard BMR equation: 10×weight + 6.25×height − 5×age (+5 for men, −161 for women).
- Five activity levels. From sedentary (×1.2) to extra active (×1.9), each with a clear description to help you choose.
- Full TDEE table. See daily needs for every activity level side by side, not just the one you picked.
- Weight-loss target. Automatically subtracts ~500 kcal/day, the classic guideline for losing about 0.5 kg per week.
- Weight-gain target. Adds ~500 kcal/day for a steady, mostly-lean bulk of about 0.5 kg per week.
- Private and free. Your body measurements never leave your browser; unlimited recalculations.
- Instant and mobile-friendly. Adjust any input and watch every number update live.
BMR vs. TDEE: what is the difference?
BMR is what you burn lying still all day — typically 60–70% of total expenditure. TDEE adds everything else: walking, working, exercising, even digesting food. Weight management runs on TDEE: eat below it to lose, above it to gain, at it to maintain. That is why the calculator leads with BMR but centers your plan on the TDEE figure for your actual lifestyle.
Using your numbers wisely
Recalculate whenever your weight changes by more than a few kilos, since BMR follows body mass. Never eat far below your BMR for extended periods without professional guidance — it is the energy your organs need. Pair calorie targets with protein and strength training to protect muscle while losing. To track body composition alongside calories, our BMI calculator gives a quick weight-status check, and the age calculator can pin down exact age inputs.
Working with pounds or inches? The unit converter switches them to metric in seconds, and the percentage calculator helps you work out macro-nutrient percentages from your calorie target.
Why the Mifflin-St Jeor Equation?
Not all BMR formulas are equal. The Mifflin-St Jeor equation — 10 × weight + 6.25 × height − 5 × age, plus 5 for men or minus 161 for women — is the formula most dietitians and researchers consider the most accurate for healthy adults, outperforming the older Harris-Benedict equation in validation studies. It needs just four inputs: age, sex, height, and weight. Because metabolism slows with age and differs by body composition, honest inputs matter more than the formula itself — a desk worker who picks ‘extra active’ gets a fantasy number. Your exact age is the first input; get it right here first.
From BMR to Your Real Daily Burn (TDEE)
BMR is what you burn lying perfectly still — typically 60–70% of your total. Real life adds walking, working, fidgeting, even digesting food, which is why the calculator multiplies your BMR by an activity factor from 1.2 (sedentary) to 1.9 (extra active) to produce TDEE: the calories you actually burn per day. Weight management runs on TDEE — eat below it to lose, above it to gain. The built-in targets apply the classic ±500 kcal guideline for roughly 0.5 kg per week. Want to sanity-check a planned deficit as a share of your intake? The percentage calculator does it in seconds.
Frequently asked questions
What is BMR?
Basal Metabolic Rate is the calories your body needs at rest to run basic functions like breathing, circulation and cell repair. It accounts for most of your daily calorie burn, which is why every diet or bulk plan starts by estimating it. This calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate formula for the general population.
How accurate is the Mifflin-St Jeor equation?
Studies find it accurate within about 10% for most healthy adults — better than the older Harris-Benedict formula. Very muscular, very lean or obese individuals and elite athletes may see larger deviations because the formula uses total weight rather than body composition. Treat the result as a strong starting estimate, then adjust based on real-world weight trends over 2–3 weeks.
What is TDEE?
Total Daily Energy Expenditure is your BMR multiplied by an activity factor — the calories you actually burn in a typical day including all movement and exercise. Eat at your TDEE to maintain weight, about 500 kcal below to lose roughly 0.5 kg per week, or 500 above to gain at a similar rate.
How many calories should I eat to lose weight?
A moderate deficit of 300–500 kcal below your TDEE typically yields 0.3–0.5 kg of fat loss per week — sustainable without extreme hunger. The calculator shows the 500-kcal-deficit figure automatically. Avoid crash deficits far below your BMR, and consult a professional if you have medical conditions.
Does muscle really burn more calories?
Yes, but modestly: muscle burns roughly 13 kcal per kg per day at rest versus about 4.5 for fat. Building a few kilos of muscle raises BMR slightly and — more importantly — improves how your body partitions a calorie surplus. Strength training plus adequate protein is the best companion to any calorie target from this tool.
Is my health data stored?
No. The calculator runs entirely in your browser; your age, weight and other inputs are never uploaded, saved or shared with anyone.
How often should I recalculate my BMR?
After meaningful weight change or every year or two — metabolism shifts with age and body composition, so old numbers drift.
Does muscle versus fat change the result?
Yes. The formula uses weight, height, age and sex, so two people at the same weight can differ; very muscular or very lean bodies see larger gaps.
What activity level should a desk worker pick?
Sedentary (×1.2) if you barely move, lightly active (×1.375) with some daily walking — most desk workers land in these two.
How It Works: Under the Hood
BMR — basal metabolic rate — is what your body burns at rest in 24 hours: breathing, circulation, cell repair, temperature regulation. This calculator uses the Mifflin-St Jeor equation, the clinical standard since 1990. Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. Women: same formula ending in − 161 instead of + 5. Weight dominates — the same age and height can still mean hundreds of calories apart.
The older Harris-Benedict equation (revised 1984) still powers many calculators. 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. Built from leaner early-20th-century subjects, it overestimates by 5–10% today — the usual reason two calculators disagree.
BMR × an activity factor = TDEE (total daily energy expenditure): 1.2 sedentary, 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 extra active (physical job plus training). The multipliers are the weakest link — most people overestimate by a full tier.
Real-World Use Cases
- Sustainable cutting: A 32-year-old man, 85 kg, 178 cm, gets a BMR near 1,755 kcal and a sedentary TDEE near 2,106 kcal. Eating 1,850 kcal/day creates a ~250 kcal deficit — about 1 kg every four weeks.
- Fueling marathon training: A 60 kg, 165 cm, 28-year-old woman has a BMR near 1,363 kcal, but at the 1.9 multiplier her TDEE hits ~2,590 kcal. Sedentary-level eating would leave a 700+ kcal hole — a recipe for injury.
- Plateau diagnosis: A woman stalled at 70 kg re-runs her numbers and finds her TDEE dropped ~90 kcal/day — a 100 kcal adjustment restarts the loss.
- Lean bulking: A 75 kg lifter with a TDEE of 2,800 kcal targets 3,050–3,100 kcal — a modest surplus that builds muscle while limiting fat.
Advanced Tips
- Pick the multiplier one tier below your ego. Training 3 days a week but sitting otherwise makes you lightly active (1.375) — inflated activity selection is this calculator’s biggest error source.
- Re-run every 5 kg of change. BMR drops roughly 50–70 kcal per 5 kg lost, so a deficit that worked at 90 kg stalls at 80 kg.
- Treat BMR as your never-go-below floor. Eating under BMR for weeks triggers adaptive thermogenesis — the body downregulates to match intake.
Common Mistakes to Avoid
- Adding exercise calories on top of an active multiplier. Selecting 1.55 already counts your workouts — a tracker’s extra 400 kcal double-counts.
- Using the wrong units. The equations need kilograms and centimeters — pounds entered as kilograms yields a BMR for a body twice your size.
- Treating TDEE as a rigid daily target. Expenditure fluctuates daily — weekly averages drive weight change, not hitting TDEE to the calorie each day.
- Expecting your smartwatch to agree. Wearables estimate via heart-rate algorithms and routinely run 15–30% high. The equation is the more reliable baseline.