The three formulas
- Mifflin-St Jeor (1990) — men = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5; women use the same formula with −161. It was built from measurements of 498 people, and the original paper reported that the 1919 Harris-Benedict equations overestimated measured values by about 5%.
- Harris-Benedict (1919, revised 1984) — the oldest. Most calculators use the 1984 Roza–Shizgal revision (men: 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age).
- Katch-McArdle — 370 + 21.6 × lean body mass (kg). It ignores sex, age and height and looks only at lean mass derived from your body fat percentage.
A 2005 systematic review in the Journal of the American Dietetic Association concluded that Mifflin-St Jeor predicted resting metabolic rate within 10% of measured values in more non-obese and obese adults than any other equation. That is why most calculators default to it today.
Same person, three answers
| Example | Mifflin | Harris-Benedict (rev.) | Katch-McArdle |
|---|---|---|---|
| Man, 41, 177 cm (5′10″), 70.2 kg (155 lb) | 1,608 kcal | 1,645 kcal | 15% fat: 1,659 / 20%: 1,583 |
| Woman, 30, 162 cm (5′4″), 58 kg (128 lb) | 1,282 kcal | 1,356 kcal | 25% fat: 1,310 / 30%: 1,247 |
Harris-Benedict usually comes out highest, and Katch-McArdle moves 70–80 kcal for every 5 points of body fat. Home body-fat scales can swing by several points depending on hydration and timing, so Katch-McArdle only helps if you trust your body-fat number.
Which one to use
- You don’t know your body fat — Mifflin. The safest default.
- You carry a lot of muscle and know your body fat fairly well — compare Katch-McArdle with Mifflin.
- Either way — the result is a starting point. Adjusting from 2–4 weeks of real weight trend matters more than the formula.
Switching formulas in the app
The Android app "Calorie Calculator" uses Mifflin-St Jeor by default.
Enter your details
On the Calculator tab, fill in sex, height, weight and age under "Your details". Tap a value to type a number directly; kg/lb and cm/ft-in can be switched in settings.
Unlock the other formulas with an ad
In settings, "BMR formula options" unlocks Harris-Benedict and Katch-McArdle permanently after one rewarded ad, and a "BMR formula" picker appears in Your details. Katch-McArdle uses the body fat from your weight log (Extra metrics, also unlocked by an ad); without it the app falls back to Mifflin.
Compare the results
Switching the formula instantly recalculates BMR, TDEE and Daily target calories.
FAQ
Why is my smart scale’s BMR different?
Body-composition scales usually estimate BMR from lean mass, which is closer to Katch-McArdle. All of these are estimates; lab measurement (indirect calorimetry) can differ.
Should I eat exactly my BMR?
No. BMR is energy at complete rest; your daily burn is TDEE. See how to pick an activity level.
Sources: Mifflin et al., Am J Clin Nutr 1990 · Frankenfield et al., J Am Diet Assoc 2005
Calorie Calculator: BMR TDEE
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