FFMI Calculator
Estimate your Fat-Free Mass Index (FFMI) and Normalized FFMI using your height, weight, and body fat percentage. Useful for tracking muscularity over time — especially when your scale weight is misleading.
FFMI Calculator
Calculates FFMI and Normalized FFMI from height, weight, and body fat %.
FFMI
21.6
Normalized FFMI
21.9
Category
Athletic
Lean Body Mass
66.3 kg
Fat Mass
11.7 kg
Inputs used
78 kg • 175.3 cm • 15%
What is FFMI?
FFMI stands for Fat-Free Mass Index. It estimates how much lean mass you carry relative to your height. Unlike weight alone, FFMI tries to separate “how big you are” into lean mass versus fat mass, using your body fat % input.
Normalized FFMI adjusts the score to a standard height so taller or shorter people can compare more fairly. The most useful way to use FFMI is as a trend metric: keep inputs consistent and watch how the number changes over time.
FFMI FAQs
It depends on body fat %, training history, and genetics. In general, higher FFMI suggests more lean mass for your height. Use FFMI to compare yourself to your past self — not as a personality test.
FFMI is based on fat-free mass (lean body mass). To estimate that, we need a body fat % to split your total weight into fat mass and lean mass. If your body fat % estimate is off, FFMI will be off too.
BMI is weight relative to height and ignores body composition. FFMI tries to measure lean mass relative to height, which is more relevant for muscularity tracking.
Use the most consistent method you have — Navy tape measurements, a smart scale (less accurate but consistent), or a photo-based AI estimate. The best input is the one you can repeat the same way every time.
No. This is a fitness calculator for educational and tracking purposes. Inputs and estimates can be imperfect. Use it as a trend tool, not a diagnosis.