HealthMath

Health calculators in your pocket — BMI, calories, body composition and water needs, all on-device.

Health calculators are estimates built on population averages, and each carries a known error. BMI cannot distinguish muscle from fat. Calorie formulas like Mifflin-St Jeor estimate resting expenditure within roughly ten percent, then multiply by an activity factor that is itself a guess.

That does not make them useless — it makes them useful as a starting point and a trend rather than a verdict. The number that matters is usually the change over time, since a consistent estimate moving in a direction tells you more than a single figure with an error bar you cannot see.