BMR Calculator (Mifflin-St Jeor)
Calculate your Basal Metabolic Rate (BMR) — the calories your body burns at complete rest — using the Mifflin-St Jeor equation, the formula the Academy of Nutrition and Dietetics identifies as the most accurate for healthy adults. The tool also estimates your TDEE (maintenance calories) for your activity level, in metric or imperial units.
Your results
Your basal metabolic rate is about:
Calories at each activity level
| Activity | Multiplier | Maintenance calories |
|---|
What is BMR?
Your Basal Metabolic Rate (BMR) is the number of calories your body burns to keep you alive while completely at rest — powering your heart, brain, lungs, and the constant cellular work of staying warm and functioning. For most people, BMR is the single largest piece of daily energy expenditure, often 60-70% of the total. Everything you do on top of that — walking, working, training — adds to it.
The Mifflin-St Jeor equation
This calculator uses the Mifflin-St Jeor equation, published in 1990 and validated repeatedly since. The Academy of Nutrition and Dietetics reviewed the major predictive equations and concluded Mifflin-St Jeor is the most accurate for estimating resting energy expenditure in healthy, non-obese and obese adults:
- Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
- Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
The tool converts your imperial inputs to metric internally, so you get the same answer whether you enter pounds and feet/inches or kilograms and centimetres.
From BMR to TDEE (maintenance calories)
BMR alone undercounts what you actually burn. To get your Total Daily Energy Expenditure (TDEE) — the calories that hold your weight steady — we multiply BMR by an activity factor from 1.2 (sedentary) up to 1.9 (extra active). The results table shows your maintenance calories at every activity level so you can see how training volume changes the number. To gain weight, eat above your TDEE; our calorie surplus calculator turns that into target calories and macros.
Sources: Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990 (PubMed) · Academy of Nutrition and Dietetics · NIH / NIDDK · Mayo Clinic — Metabolism.
Frequently asked questions
- What is a normal BMR?
- It varies widely with size, age, and sex, but a typical adult BMR falls roughly between 1,200 and 1,900 kcal per day. Larger and younger people, and men on average, have higher BMRs. Enter your stats above for your specific estimate.
- Is BMR the same as TDEE?
- No. BMR is calories burned at rest; TDEE adds the energy from daily activity and exercise. TDEE is always higher and is the number you compare your intake against to maintain, gain, or lose weight.
- Which BMR formula is most accurate?
- The Mifflin-St Jeor equation, used here, is the most accurate widely-validated predictive formula for healthy adults according to the Academy of Nutrition and Dietetics. It still carries about a 10% margin of error.
- Should I eat below my BMR to lose weight?
- Generally no. Eating below BMR for extended periods is not recommended and should only be done under medical supervision. For weight management, adjust intake relative to TDEE, not BMR.
- How do I use my BMR to gain weight?
- Find your TDEE (BMR times your activity factor), then eat above it. A surplus of 250-500 kcal supports a steady, lean gain. Our surplus and weight gain calorie calculators handle this for you.