FFMI Calculator
FFMI measures how much lean mass you carry relative to your height. Enter your weight, height and body-fat percentage to see your FFMI, your height-normalized score, and where you sit on the athlete reference scale.
FFMI Calculator
FFMI measures how much lean mass you carry relative to your height. Enter your weight, height and body-fat percentage to see your FFMI, your height-normalized score, and where you sit on the athlete reference scale.
Educational fitness metric only — not a health diagnosis. If you are unsure of your body-fat percentage, estimate it first with the Body Fat Calculator.
Not sure? Estimate it with the Body Fat Calculator.
- Below average
- Average
- Above average
- High
- Very high
- Normalized FFMI (height-adjusted)
- 20.3
- Lean body mass (LBM)
- 61.2 kg
- Body fat mass
- 10.8 kg
FFMI = lean body mass ÷ height². Normalized FFMI adds a height correction so shorter and taller lifters can be compared fairly. Values above ~25 are uncommon for natural athletes and often point to a body-fat measurement error — treat extreme numbers as a prompt to re-check your input, not as a judgment.
This is an educational estimate, not medical advice. Consult a qualified professional.
Save & share your result
What is FFMI?
Fat-Free Mass Index (FFMI) is your lean body mass divided by your height in metres squared. It is similar in shape to BMI, but instead of comparing total body weight it compares only your fat-free mass — muscle, bone, organs and water. That makes it more meaningful for athletes and lifters, who can be heavy but metabolically healthy because of extra muscle.
Because taller people have more frame to fill, FFMI also includes a height correction (the “normalized” score) so a 165 cm lifter and a 195 cm lifter can be compared on the same scale.
How the calculation works
First we subtract your fat mass from your total weight to get lean body mass (LBM). Then we divide LBM by height² to get FFMI. The normalized version adds 6.1 × (1.8 − height in metres) to correct for stature.
The formulas are:
- LBM = weight × (1 − body fat %)
- FFMI = LBM ÷ height(m)²
- Normalized FFMI = FFMI + 6.1 × (1.8 − height m)
Reading your result
The reference bands are calibrated to common population and athlete data. Most untrained adults fall in the 17–19 range; trained natural lifters often sit around 20–23. Values above ~25 are very unusual for natural athletes and usually mean the body-fat estimate is too low, so re-check your input before drawing any conclusion.
FFMI is best used to track your own progress over time, not to compare yourself to outliers online.
Frequently asked questions
What is a good FFMI?
For most men, 18–20 is average, 20–22 is athletic, and 22–25 is highly muscular. For women, subtract roughly 1.5–2 points because of higher essential body fat. The most useful comparison is your own trend over time.
Why normalize FFMI for height?
Taller people naturally have more bone and muscle mass. The normalized score adds a height correction so FFMI can be compared fairly across short and tall individuals.
Can FFMI tell if someone is natural?
No. Extremely high values are uncommon for natural athletes, but they can also come from an inaccurate body-fat estimate, unusual genetics, or measurement error. FFMI is not a diagnostic or judgment tool.
How do I estimate body-fat percentage?
You can use the Body Fat Calculator here, which estimates body fat from a few tape measurements, or a reliable smart scale, DEXA scan, or skinfold callipers for a more accurate number.
Sources & references
Not medical advice. This result is an educational estimate from HealthyLifeStyles (Trusted Wellness), based on population formulas — not a diagnosis or treatment. Always consult a qualified healthcare professional about your health.
https://www.healthylifesstyles.com/tools/ffmi-calculator