Health calculators

Plain-English health math.

Free calculators for the health questions worth asking yourself — with the disclaimers most tools skip. BMI live now, the rest shipping over the next few weeks.

Tools

BMI calculator

Body mass index with both WHO general and Asian-population thresholds. Includes the disclaimer most tools skip.

Running pace

Pace + splits + race-time predictor (Riegel). Marathon, half, 10K, 5K presets.

Erg calculator

Concept2 RowErg / SkiErg / BikeErg — watts ↔ split ↔ time ↔ distance.

BMR calculator

Basal metabolic rate via Mifflin-St Jeor (modern standard) + Harris-Benedict side-by-side.

TDEE calculator

Total daily energy expenditure — BMR × activity multiplier with sensitivity ranges across all activity levels.

Macro calculator

TDEE → cut/maintain/bulk calorie target → protein/carb/fat split with adjustable ratios.

A note on what these tools are

Every health calculator on this hub is a screening tool, not a diagnosis. They simplify population-level math into single numbers; the numbers correlate with health outcomes at the population level but say less about any individual than most calculators imply.

We try to make this clear in each tool's copy — what the formula knows, what it doesn't, what to pair it with. If a calculator tells you something concerning, talk to a doctor. If it tells you something reassuring, that's still not a substitute for one.

Don't see the calculator you need?

We're shipping new health tools constantly. Request a tool — a 30-second form straight to the founder. No marketing list, no data tracking.