Lean: Body Fat & BMI Tracker

Most body-fat apps run on guesswork. Lean is the opposite — every number
comes from a published formula, cited on screen, so you can check the
source yourself. No account, and your numbers never leave your device.

WHAT LEAN CALCULATES

- Body fat % using the U.S. Navy circumference method (Hodgdon & Beckett, 1984)
- Lean body mass and fat mass in lb or kg
- BMI, with the standard category bands
- BMR using Mifflin-St Jeor (Am J Clin Nutr, 1990)
- TDEE across five activity levels
- Reference weight at your current lean mass

MEASURE, DON'T GUESS

The Navy method needs a tape measure and three numbers: waist at the
navel, neck, and — for women — hips at the widest point. No calipers,
no scale beyond your usual one, no lab visit. Enter your measurements
and every result updates at once.

TRACK CHANGE OVER TIME

Save a measurement and Lean keeps it. The Progress tab shows how body
fat, lean mass and weight have moved, so you can see whether a training
block or a calorie deficit is actually working.

EVERY FORMULA IS CITED

Tap "How this is calculated" on any result and Lean shows the formula
it used and the published source. Nothing is a black box, and nothing
is invented.

PRIVATE BY DESIGN

Lean has no account, no login, and no server. Your measurements are
stored on your device and are never uploaded. The app works fully
offline.

Lean is free and supported by advertising.