Crunch BMR Calculator
Most BMR calculators quietly use one formula. This one runs all three major equations — Mifflin-St Jeor, Harris-Benedict and body-fat-based Katch-McArdle — so you can see the range, then turns each into TDEE by activity.
How it works
BMR is the energy your body burns at complete rest — breathing, circulation, cell repair. Mifflin-St Jeor (1990): 10×kg + 6.25×cm − 5×age + 5 (men) or − 161 (women). Harris-Benedict (revised 1984) uses different coefficients and tends to read slightly higher. Katch-McArdle skips sex and age entirely: 370 + 21.6 × lean body mass, so it wins when body composition is unusual — very muscular or very high body fat. Multiply any BMR by 1.2–1.9 for activity to get TDEE, your real daily burn.
Frequently asked questions
Which BMR formula should I trust?
For most adults, Mifflin-St Jeor — it performed best in validation studies and is the dietitian default. If you know your body-fat percentage accurately and your build is far from average, Katch-McArdle may be closer. Comparing all three, as this calculator does, shows you the realistic range.
What is a good BMR?
There is no single "good" number — BMR scales with size. Adult men commonly fall between 1,600 and 2,000 kcal/day and women between 1,300 and 1,600, but a tall, heavy person will naturally sit above those ranges. What matters is how it compares to your intake and activity.
What is the difference between BMR and TDEE?
BMR is rest-only burn. TDEE (total daily energy expenditure) is BMR multiplied by your activity factor — 1.2 for sedentary up to 1.9 for athletes — and is the number that actually maintains your weight.
How do I measure my body fat for Katch-McArdle?
Options range from DEXA scans and smart scales to skinfold calipers and the US Navy tape-measure method. Even a rough estimate helps: at 80 kg, the difference between 15% and 25% body fat changes the Katch-McArdle result by about 170 kcal.
🔥 From BMR to a full eating target
The Calorie Calculator adds goals and macro splits on top of your TDEE.