BMR Calculator
Calculate your Basal Metabolic Rate — the calories your body burns at complete rest — using three industry-standard formulas, plus TDEE estimates for every activity level.
| Activity Level | Multiplier | TDEE (kcal/day) | Weekly Total |
|---|---|---|---|
| Enter your details to see results | |||
* TDEE is based on the Mifflin-St Jeor BMR. For informational purposes only — not medical advice.
Calculate your Basal Metabolic Rate — the calories your body burns at complete rest — using three widely used clinical formulas: Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.
How BMR Calculator Works
Mifflin-St Jeor (the calculator's primary result) is: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, or −161 instead of +5 for women. It is generally considered the most accurate equation for the general population and is the version most modern dietitians default to.
Harris-Benedict (revised 1984 version) uses a different set of coefficients — for men, 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age — and tends to run slightly higher than Mifflin-St Jeor for most body types, since it was derived from an older, different reference population.
Katch-McArdle instead uses lean body mass rather than total weight: BMR = 370 + 21.6 × LBM(kg), where LBM is estimated from your entered body fat percentage (LBM = weight × (1 − body fat% ÷ 100)). This can be more accurate for people who know their body fat percentage and have an atypical muscle-to-fat ratio, since it does not simply assume a "typical" body composition for your weight.
See It In Action
Who Uses BMR Calculator and Why
- Comparing your resting metabolism across three different clinical formulas before choosing a calorie target.
- Getting a Katch-McArdle estimate that accounts for your known body fat percentage rather than assuming a typical build for your weight.
- Understanding why a nutrition app or another calculator gave a noticeably different resting-metabolism number.
Mistakes to Avoid
- Entering an inaccurate body fat percentage into the Katch-McArdle field — since that formula relies entirely on lean mass, a rough guess can throw the result off more than the other two formulas, which only need height, weight, and age.
- Assuming BMR is the number you should eat — BMR is calories burned at complete rest, well below your actual daily needs once activity is factored in.
- Picking whichever of the three results is highest because it allows more food, rather than considering which formula best fits your situation.
Tips for Best Results
- If you don't have a reliable body fat percentage, lean on the Mifflin-St Jeor figure — it's generally considered the most accurate for the general population and doesn't require that extra input.
- If you know you have an atypical build (very muscular or very lean), the Katch-McArdle estimate is worth weighing more heavily, since it's less influenced by a "typical" body composition assumption.
Fixing Common Problems
The three formulas gave me noticeably different numbers. — This is expected — each was derived from a different research population and input set. A spread of 100-150 kcal between the three is normal; use Mifflin-St Jeor as your default unless you have a strong reason to prefer another.
Terms Explained
BMR (Basal Metabolic Rate): The calories your body burns at complete rest just to maintain basic functions like breathing and circulation.
Lean body mass (LBM): Total body weight minus fat mass — the input the Katch-McArdle formula uses instead of total weight.