Nearly every BMR calculator online defaults to a single formula and never mentions there's a better option for some people.
Mifflin st jeor calculator, the default for good reason
Mifflin-St Jeor is considered the most broadly accurate formula for the general population, using just sex, age, height, and weight. For an 80 kg, 180 cm, 30-year-old male, it gives 1,780 calories/day at complete rest.
Katch mcardle calculator, when you know your body fat %
Katch-McArdle uses lean body mass instead of total weight — more accurate if you actually know your body fat percentage from a DEXA scan or a reliable test. For the same person at 18.75% body fat (65 kg lean mass), it gives 1,774 calories/day — close here, but the two formulas can diverge more for people with body compositions far from average.
Bmr vs tdee, why BMR alone isn't your calorie target
BMR is calories burned at complete rest, before any movement — it's not what you should eat. Multiply it by an activity factor (or use a TDEE calculator) to get your real daily calorie needs.
