Basal Metabolic Rate (BMR) Calculator
Estimate how many calories your body burns at complete rest, using either the Mifflin-St Jeor or Harris-Benedict equation.
Your Basal Metabolic Rate
Enter your details and we'll estimate your resting metabolic rate.
How it works
Basal Metabolic Rate (BMR) is the number of calories your body needs just to stay alive — powering your heart, brain, kidneys, breathing and cellular repair while you rest. It's the single biggest chunk of your daily energy budget, typically 60–70% of everything you burn, and knowing it is the starting point for any sensible nutrition plan.
This calculator is useful whether you're trying to lose weight, build muscle, recover from illness, or simply understand where your calories go. Nutritionists, personal trainers and clinicians all use BMR as a baseline before adding activity to reach a total daily calorie target.
How it works
We offer two well-established equations. Both take weight, height, age and sex as inputs and return an estimate of resting energy expenditure in calories per day.
- Mifflin-St Jeor (1990) — the modern standard, endorsed by the American Dietetic Association.
Men:10 × kg + 6.25 × cm − 5 × age + 5
Women:10 × kg + 6.25 × cm − 5 × age − 161 - Harris-Benedict (revised, 1984) — older but still widely cited. Tends to run slightly higher for men.
We then multiply by an activity factor between 1.2 (sedentary) and 1.9 (very physical work plus training) to give a daily maintenance estimate.
A worked example
A 40-year-old woman, 168cm tall, 70kg, moderately active:
BMR = (10 × 70) + (6.25 × 168) − (5 × 40) − 161 = 700 + 1,050 − 200 − 161 = 1,389 kcal.
Maintenance at ×1.55 ≈ 2,153 kcal.
Why this matters
Undereating below BMR for weeks at a time is a common — and counterproductive — dieting mistake. It slows metabolism, erodes muscle and usually ends in a rebound. Knowing your BMR sets a sensible floor for your calorie intake and a realistic ceiling for how big a deficit is worth chasing.
Common mistakes
- Confusing BMR with daily calorie needs and eating far too little.
- Using outdated weight or height figures — recalculate every few kilos of change.
- Overestimating activity level, which inflates the maintenance number.
- Ignoring changes to muscle mass — a strength-training year raises BMR meaningfully.
- Treating the formula result as exact rather than as an estimate ±10%.
- Comparing your BMR to someone else's without accounting for age, size and body composition.
Educational only — not a substitute for personalised advice from a doctor or registered dietitian, particularly if you have a medical condition affecting metabolism.
Related tools: Calorie Needs Calculator · BMI Calculator · Body Fat Calculator · Ideal Weight Calculator