acalculator

What is my FFMI?

Calculate fat-free mass index (FFMI) to assess muscle mass and body composition. Fitness tracking tool.

Your numbers

Units
Sex
Normalized FFMI
22.09

Your normalized FFMI is 22.09 (FFMI 21.95).

FFMI
21.95
Fat-free mass
153 lb
Fat mass
27 lb
Compared with Kouri et al.
Within the 25.0 limit of steroid-free athletes

Normalized FFMI: 22.09. Your normalized FFMI is 22.09 (FFMI 21.95).

Normalized FFMI by body fat

This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use

How to calculate

Computes fat-free mass index (lean mass in kg ÷ height in m squared) and the height-normalized FFMI of Kouri et al. (1995) from height, weight, and body fat.

Example with the default inputs (Sex Male, Height 5 ft 10 in, Weight 180 lb, Body fat 15%): Your normalized FFMI is 22.09 (FFMI 21.95).

Method: FFMI = weight × (1 − body fat ÷ 100) ÷ height²; normalized FFMI = FFMI + 6.3 × (1.80 − height), weight in kg, height in m (Kouri et al. 1995).

  • The result is only as good as the body fat percentage you enter.
  • The 25.0 reference is the upper limit Kouri et al. (1995) found in 74 male athletes who had not used steroids. There is no matching published limit for women.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Sex Male, Height 5 ft 10 in, Weight 180 lb, Body fat 15% gives FFMI 21.952989, Normalized FFMI 22.091589, Fat mass 27 lb, Compared with Kouri et al. Within the 25.0 limit of steroid-free athletes.Source: Kouri et al. (1995): lean mass 81.647 × 0.85 = 69.400 kg
  2. Sex Female, Height 5 ft 5 in, Weight 132.3 lb, Body fat 25% gives FFMI 16.528926, Normalized FFMI 17.473926, Fat-free mass 99.2 lb.Source: Kouri et al. (1995) definition: 60 × 0.75 = 45 kg
  3. Sex Male, Height 5 ft 10.9 in, Weight 198.4 lb, Body fat 10% gives FFMI 25, Normalized FFMI 25, Compared with Kouri et al. Within the 25.0 limit of steroid-free athletes.Source: Kouri et al. (1995): 81 kg ÷ 1.8² = 25.0, no height correction at 1.80 m
  4. Sex Male, Height 5 ft 6.9 in, Weight 209.4 lb, Body fat 8% gives Normalized FFMI 30.872215, Compared with Kouri et al. Above the 25.0 limit of steroid-free athletes.Source: Kouri et al. (1995): 95 × 0.92 = 87.4 kg

How FFMI is worked out

Weight is in kilograms and height in metres; the calculator converts pounds, feet, and inches for you.

  • Fat mass = weight × body fat ÷ 100
  • Fat-free mass = weight − fat mass = weight × (1 − body fat ÷ 100)
  • FFMI = fat-free mass ÷ height²
  • Normalized FFMI = FFMI + 6.3 × (1.80 − height)

The normalization (Kouri et al. 1995) brings every height to the FFMI of a 1.80 m person. At exactly 1.80 m the two numbers are the same; shorter people get a small addition, and taller people a small subtraction.

Kouri et al. reference (men)

Kouri et al. (1995) measured 157 male athletes. The normalized FFMI of the 74 who had not used anabolic steroids went up to a well-defined limit of 25.0. For men, the calculator says whether your normalized FFMI is within that limit (25.0 or less) or above it. It gives no such line for women, because the study measured men only.

Assumptions

  • The result depends on the body fat percentage you enter.
  • Body fat can be 2% to 70%. Below 2% there is no answer: no one has less than the essential fat, which starts at 2% for men (American Council on Exercise).
  • Values are not rounded between steps.

Worked examples by hand

Man, 5 ft 10 in, 180 lb, 15% body fat. 180 lb = 81.6466 kg and 70 in = 1.778 m. Fat-free mass = 81.6466 × 0.85 = 69.400 kg; fat mass = 12.247 kg (27 lb). FFMI = 69.400 ÷ 1.778² = 69.400 ÷ 3.16128 = 21.95. Normalized = 21.95 + 6.3 × (1.80 − 1.778) = 21.95 + 0.139 = 22.09, within 25.0.

Woman, 1.65 m, 60 kg, 25% body fat. Fat-free mass = 60 × 0.75 = 45 kg. FFMI = 45 ÷ 2.7225 = 16.53. Normalized = 16.53 + 6.3 × 0.15 = 16.53 + 0.945 = 17.47.

Man, 1.80 m, 90 kg, 10% body fat. Fat-free mass = 81 kg. FFMI = 81 ÷ 3.24 = 25.0, and the normalized FFMI is also 25.0 (no correction at 1.80 m): exactly at the limit, so within it.

Man, 1.70 m, 95 kg, 8% body fat. Fat-free mass = 87.4 kg. FFMI = 87.4 ÷ 2.89 = 30.24. Normalized = 30.24 + 6.3 × 0.10 = 30.87, above 25.0.

Other questions people ask

What is FFMI?

FFMI stands for Fat Free Mass Index, which measures the amount of lean mass relative to height. It's an alternative to Body Mass Index (BMI) that focuses on lean mass rather than total body weight.

How is FFMI calculated?

FFMI is calculated using the formula: FFMI = (Lean Weight in kg) / (Height in meters)². The calculation involves determining your total body fat mass, calculating your lean mass (total weight minus body fat), and dividing lean mass by height squared.

What's the difference between FFMI and Normalized FFMI?

FFMI is the raw calculation of lean mass relative to height. Normalized FFMI adjusts the value to a height of 1.80 m, so people of different heights can be compared: normalized FFMI = FFMI + 6.3 × (1.80 − height in meters). The adjustment comes from Kouri et al. (1995).

What is a high FFMI?

In Kouri et al. (1995), the normalized FFMI of 74 male athletes who had not used anabolic steroids went up to a limit of 25.0, and pre-steroid-era Mr. America winners averaged about 25.4. Many steroid users in the study were above 25, and some above 30. The study is small and its authors call the findings preliminary. There is no matching published limit for women.

How accurate is the FFMI calculation?

FFMI calculation accuracy depends on the accuracy of your body fat percentage measurement. The most accurate methods include DEXA scans, hydrostatic weighing, or BodPod testing. Skinfold calipers and bioelectrical impedance scales provide reasonable estimates for most people.