TOOL C-01 — BODY COMPOSITION
Plan the change, not just the weight.
A goal body-fat percentage is more useful when you can see what it means in lean and fat mass. Put in three numbers and get a target weight, a fat-loss figure and a composition bar.
- Inputs
- Weight · current body fat · goal body fat
- Output
- Target weight · lean mass · fat to lose
- Pairs with
- Hydrostatic body-fat testing
- Units
- lb or kg
Your inputs
This assumes your lean mass stays the same — the goal is to lose fat, not muscle. Use it as a planning question for your coach, not a promise.
Target weight at goal body fat
Holding 135 lb of lean mass while body fat moves from 25% to 18%.
- Lean mass to keep
- 135 lb
- Fat to lose
- 15.4 lb
Estimates only — ask a coach before planning a cut. Hydrostatic testing measures the real number this planner is approximating.
THE METHOD
The assumption behind the planner.
The planner holds lean mass constant. It assumes the goal is to lose fat while keeping the muscle you have, which is the right question during a rebuild. In practice, some lean mass can move, especially on an aggressive plan.
That is why the result is a planning number, not a promise. A hydrostatic test measures your actual body fat; the planner helps you frame the conversation before the test and see whether a goal is realistic.
Use the body fat measurement you trust most. A smart-scale estimate can be off, and mixing methods between checks makes progress hard to read.
FORMULA
- Lean mass = weight × (1 − current body fat %)
- Target weight = lean mass ÷ (1 − goal body fat %)
- Fat to lose = (weight − lean mass) − (target weight − lean mass)
TURN THE ESTIMATE INTO A NUMBER
Measure the real number.
The planner is an estimate. Hydrostatic testing measures body fat underwater, reviews the result with your coach, and gives you a baseline worth comparing against.