FFMILab

FFMI Calculator

Adjusted FFMI: how much of your mass is muscle relative to height.

Weight (kg)

Height (cm)

Body fat %

FFMI (adjusted)

21.584

Natural genetic ceiling ≈ 25. Above 26 is unusual without PEDs.

What you entered

Weight (kg): 80Height (cm): 178Body fat %: 15%

1
Lean mass = weight × (1 − body fat %)
80 × (1 − 15/100)= 68.0 kg
2
Divide by height² (metres)
68.0 ÷ 1.78²= 21.46
3
Height-normalize (adjusted FFMI)
+ 6.1 × (1.8 − 1.78)= 21.58

Result

FFMI (adjusted): 21.584

At 80 kg, 178 cm, and 15% body fat, your adjusted FFMI is 21.58.

Fat-free mass index at common body fat levels

FFMI is lean mass divided by height in metres squared. It answers a question BMI cannot: how much muscle you carry for your frame.

Weight	Height	Body fat	FFMI
70 kg	175 cm	12%	20.4
75 kg	178 cm	10%	21.4
80 kg	180 cm	15%	21.0
85 kg	180 cm	20%	21.0
90 kg	185 cm	18%	21.3

Around 18 is average for untrained men, 20 to 22 is well trained, and figures above roughly 25 are rarely reached without performance-enhancing drugs. Scales for women run about 3 points lower. General wellness information only, not medical advice. Discuss any health decision with a qualified clinician.

BMI's more muscle-aware cousin

FFMI adjusts fat-free mass for height the same way BMI adjusts weight, giving a fairer comparison of muscularity across different heights than raw muscle mass alone.

The natural-limit benchmark

An FFMI around 25 is considered a realistic upper limit for most natural (non-enhanced) male lifters — values noticeably above that are one of the signals researchers use when studying anabolic steroid use in bodybuilding.

Frequently asked questions

What is a good FFMI score?

For men: 18–20 is average, 20–22 is above average/regular gym-goer, 22–23 is advanced, 24–25 is near the natural limit, and 25+ is exceptional (rarely achieved without enhancement). For women: subtract about 3–4 points from each range. An FFMI of 20 for a man who doesn't lift is already decent.

What FFMI is achievable naturally?

Research by Kouri et al. (1995) found that natural male bodybuilders rarely exceed an adjusted FFMI of 25, while steroid users averaged 25+. The natural ceiling depends on genetics, training years, and height — shorter lifters can sometimes exceed 25 naturally. Most natural lifters plateau around 22–24.

How do I calculate FFMI?

FFMI = (lean mass in kg) ÷ (height in m)². Adjusted FFMI adds a height correction: FFMI + 6.1 × (1.8 − height in m). You need to know your body fat percentage first. Example: 80 kg, 15% body fat, 1.78 m tall → lean mass = 68 kg → FFMI = 68 ÷ 1.78² = 21.5 → adjusted = 21.5 + 6.1 × 0.02 = 21.6.