Discover your Basal Metabolic Rate — the calories your body burns just keeping you alive.
Your body's idle engine — and why it burns most of your calories.
Your Basal Metabolic Rate is the energy your body needs at complete rest — lying still, awake, in a comfortable temperature. It powers everything you don't think about: heartbeat, breathing, brain activity, cell repair, and body temperature.
This calculator uses the Mifflin-St Jeor equation, considered the most accurate BMR formula by the Academy of Nutrition and Dietetics:
Here's the surprising part: your BMR accounts for 60–75% of all the calories you burn in a day. Exercise is a much smaller slice than most people assume.
| Organ / Tissue | Share of BMR |
|---|---|
| 🧠 Brain | ~20% |
| 🫀 Liver | ~20% |
| 💪 Muscles (at rest) | ~20–25% |
| ❤️ Heart | ~10% |
| 🫘 Kidneys | ~7% |
| Other tissues | ~20% |
Your brain alone burns roughly 300+ kcal per day — thinking hard really is work. This is why simply existing costs more energy than any workout.
These two numbers are often confused, but they answer different questions:
For weight goals, always use TDEE. Eating below your BMR for long periods can trigger muscle loss, fatigue, and metabolic adaptation — your body literally slows down to match the low intake. A smarter deficit is 400–500 kcal below your TDEE, which the activity breakdown above shows for your BMR.
Yes — modestly, and mostly through one lever: muscle. Strength training 2–4 times per week builds tissue that burns calories around the clock. Gaining 3 kg of muscle raises your resting burn by roughly 40 kcal/day — not huge, but it compounds over years and makes maintaining your weight noticeably easier.
Other helpful habits: eat enough protein (digesting it burns more calories than carbs or fat), sleep 7–9 hours, stay hydrated, and avoid extreme diets. What doesn't work: "metabolism-boosting" supplements, spicy foods, and ice water — their effects are tiny and temporary.
Quick answers to common BMR questions.
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep your heart beating, lungs breathing, brain working, and body temperature stable. It typically accounts for 60–75% of your total daily calorie burn.
There's no single "good" BMR — it depends on your size, age, and gender. Average BMRs are roughly 1,400–1,800 kcal for women and 1,600–2,000 kcal for men. A higher BMR simply means a bigger or more muscular body, not a healthier one.
BMR is what you burn at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR plus all movement — walking, working, exercising, even fidgeting. TDEE is the number that matters for setting calorie targets.
Yes, but mainly because people lose muscle as they age. Research shows BMR stays fairly stable from age 20 to 60 when muscle mass is maintained — strength training is the best defense against metabolic slowdown.
Yes, modestly. Building muscle is the most effective way — each kg of muscle burns roughly 13 kcal per day at rest. Regular exercise, adequate protein, good sleep, and avoiding crash diets all help maintain a healthy metabolism.
Generally no. Your calorie target should be based on your TDEE (BMR plus activity), not your BMR. Eating below your BMR for extended periods can lead to muscle loss, fatigue, and metabolic adaptation. A 500 kcal deficit below TDEE is the safer approach.
No. All calculations run entirely in your browser. Your details and results are never stored or sent anywhere.
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