FFMI Calculator
Fat-Free Mass Index calculator for men and women
Free FFMI Calculator – Fat-Free Mass Index for Men and Women
Fat-Free Mass Index and normalized FFMI
FFMI means Fat-Free Mass Index: a score of how much muscle you carry relative to your height. The Fat-Free Mass Index (FFMI) is often more useful than BMI for people who lift, because it measures muscle relative to height rather than total weight. Enter your height, weight and body fat percentage and this calculator works out your fat-free mass, your FFMI and a normalized FFMI that adjusts for height so people of different sizes can be compared fairly. If you do not know your body fat, use our body fat calculator first, then come back. Everything is calculated privately in your browser.
Features
Muscularity Index
Measures lean mass relative to height, not just bodyweight.
Normalized FFMI
Adjusts for height so results are comparable across body sizes.
Works With Body Fat
Links to our body fat calculator if you need your percentage first.
Private & Free
No account and nothing leaves your device.
FFMI Charts, Formula & Example
FFMI chart — men (normalized)
- 16-17 — below average
- 18-19 — average
- 20-21 — athletic
- 22-23 — excellent
- 25+ — elite (debated natural limit); women run ~4-5 points lower
FFMI chart — women (normalized)
- 13–14 — below average
- 15–16 — average
- 17–18 — athletic
- 19–21 — excellent
- 22+ — exceptional, rarely reached naturally
The formula
- Fat-free mass (FFM) = weight × (1 − body fat%)
- FFMI = FFM ÷ height² (m)
- Normalized FFMI = FFMI + 6.1 × (1.8 − height)
- Normalization makes different heights comparable
Worked example
- Man, 180 cm, 85 kg, 15% body fat
- Fat-free mass = 85 × 0.85 = 72.25 kg
- FFMI = 72.25 ÷ 1.80² = 22.3
- Normalized = 22.3 + 6.1 × (1.8 − 1.8) = 22.3 → excellent
Guides
- What Is BMI and How Is It Calculated?Where BMI falls short for muscular people
- How to Calculate Your Daily Calorie Needs (TDEE)Set a surplus to raise your FFMI
Frequently Asked Questions
What does FFMI mean?
FFMI stands for Fat-Free Mass Index. It divides your fat-free mass (everything that is not fat: muscle, bone, organs, water) by your height squared, giving a muscularity score that, unlike BMI, is not inflated by body fat.
How do I calculate FFMI by hand?
Multiply your weight by (1 − body fat %) to get fat-free mass in kg, then divide by your height in metres squared. For the normalized value add 6.1 × (1.8 − height in m). Example: 85 kg at 15% and 1.80 m → 72.25 ÷ 3.24 = 22.3.
What is a good FFMI?
For men, a normalized FFMI around 18–20 is average, 20–22 is athletic and 22–25 is excellent. Values above about 25 are rare naturally. Women's ranges are roughly 2–3 points lower.
What does normalized FFMI mean?
Normalized FFMI adjusts your score to a reference height of 1.8 m so that taller and shorter people can be compared on the same scale.
Do I need my body fat percentage?
Yes, FFMI is based on fat-free mass, which requires your body fat percentage. If you don't know it, use the body fat calculator linked on this page and enter the result here.
Is FFMI better than BMI?
For athletic or muscular people, FFMI is usually more informative because it separates muscle from fat. For general health screening, BMI is still a quick and useful measure.
What's a good FFMI for women?
For women, 13-15 is about average, 16-17 athletic, and 18+ is considered very muscular — roughly 4-5 points below the men's ranges.
How do I increase my FFMI?
By gaining muscle: consistent resistance training, enough protein (≈1.6-2.2 g/kg) and a moderate calorie surplus, while keeping body fat in check.