How to use this calculator
- Enter weight, waist, neck, and height measurements.
- Use consistent tape-measure placement.
- Review estimated body fat, lean mass, and target-weight guidance.
#1487 · Health Tool
Diet Body Fat Calculator
Estimate body fat and translate it into a diet plan. This calculator uses height, weight, waist, and neck measurements to approximate body composition, target weight, fat loss needed, and progress timeline.
Calculator
Body composition inputskg
cm
cm
cm
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What the result means
The result estimates body composition and shows how much fat reduction may be needed to reach a healthier target range.
Simplified body fat estimate uses a Navy-style log formula. Lean mass = weight × (1 − body fat%). Target weight = lean mass ÷ (1 − target body fat%).
Tape-based formulas are estimates. For precision, compare trends over time or use professional body composition testing.
Example calculation
An 82 kg person with 90 cm waist, 40 cm neck, and 178 cm height may estimate around 22% body fat and a target weight near 76 kg for 16% body fat.
Tips for better results
- Measure waist at the same time of day.
- Preserve lean mass with protein and strength training.
- Track body fat trends rather than one measurement.
FAQ
What body fat percentage is healthy?
Healthy body fat ranges vary by sex, age, and athletic status, but moderate ranges generally carry lower risk than very high levels.
How much body fat should I lose?
The amount depends on current body fat, target range, lean mass, and a sustainable timeline.
Is body fat better than BMI?
Body fat estimates can be more informative than BMI for muscular people, but both have limitations.
What is FFMI?
FFMI is fat-free mass index, a way to compare lean mass relative to height.
How long does it take to lose body fat?
A sustainable timeline often targets moderate weekly fat loss while preserving lean mass.
Related calculators
Diet Body Fat Modules
| Module | Purpose |
|---|---|
| Body Fat Estimate | Approximates current body fat percentage. |
| Lean Mass | Calculates estimated fat-free mass. |
| Target Weight | Projects target weight from goal body fat. |
| Timeline | Estimates weeks needed for fat reduction. |
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