Fat-Free Mass Index (FFMI) Calculator
Measure how muscular you are for your height with FFMI and the normalized FFMI.
Body CompositionScience-backed formula
Enter your details
Fill in the fields, then calculate
Enter your weight.
Enter your height.
Enter your body fat percent.
Awaiting Data
Enter your details and tap Calculate to see your results appear here.
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ResultYour result appears here.
What it measures
FFMI scores your lean mass against your height. It tells muscle apart from size, where BMI cannot.
Your measurements become one clear number you can track over time.
The normalized version adjusts for height so tall and short lifters compare fairly.
How to use this calculator
- Enter your sex, weight, and height.
- Add your body fat percentage.
- Tap Calculate for FFMI and normalized FFMI.
The formula used
FFMI = (weight × (1 − body fat)) / height(m)²
Normalized = FFMI + 6.1 × (1.8 − height in m)
Normalized = FFMI + 6.1 × (1.8 − height in m)
- weight
- Body weight in kg.
- body fat
- Your body fat as a fraction.
- height
- Height in metres.
Understanding Your Results
Below average
Under 18
Room to build muscle.
Average
18 to 20
A typical untrained range.
Athletic
20 to 23
Well-muscled.
Near natural limit
23 to 25
High natural muscularity.
Tips to Improve
- Train with progressive overload.
- Eat enough protein and calories.
- Track FFMI alongside body fat.
- Be patient; muscle grows slowly.
Frequently Asked Questions
Around 25 for men, though genetics shift this. Values well above can suggest enhancement.
Yes. FFMI depends on lean mass, which needs body fat to calculate.
Yes. Women typically score lower because of higher essential fat.
Scientific References
- Kouri, E. M., et al. (1995). Fat-free mass index in users and nonusers of anabolic steroids. Clinical Journal of Sport Medicine, 5(4), 223–228.
- Schutz, Y., et al. (2002). Fat-free mass index and fat mass index percentiles. International Journal of Obesity, 26(7), 953–960.