
BMI & body composition
Reads your height and weight against the standard ranges, and says plainly where BMI stops being a useful signal for you.
- in
- Height, weight, optional waist
- out
- Index, range, waist ratio
Our guides keep quoting numbers — a deficit, a protein floor, a litre count, a bedtime. These are the instruments that work them out for your body instead of an average one. Enter what you know, read what it means.
24.6kg/m²
Healthy range
Each one is calibrated against the same evidence its desk is written from. All five are fitted and running, and every reading is worked out in your own browser.

Reads your height and weight against the standard ranges, and says plainly where BMI stops being a useful signal for you.

Estimates the energy you burn on an average day, then sets a deficit you can actually hold for months instead of a fortnight.

Turns your bodyweight and training load into a protein floor, then divides the rest of the day between carbohydrate and fat.

Works out a realistic daily fluid figure from your size, your climate and how hard you sweat — food and coffee counted in.

Counts backwards in ninety-minute cycles so you wake between them, and tells you the latest useful time for coffee.
Every instrument shows its working. You will see the formula it used, the assumptions baked into it, and how wide the error bars really are — because a population equation applied to one body is an estimate, not a measurement.
Nothing here is a diagnosis. Pregnancy, diagnosed conditions, eating disorders and prescribed medication all change these numbers, and each instrument says where to stop reading and start talking to someone who knows your history.