# What is my FFMI?

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.

- Page: https://www.acalculator.org/health/ffmi-calculator
- JSON spec: https://www.acalculator.org/health/ffmi-calculator.json
- Version: 23af40b7f479

## Default answer

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).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| sex | Sex | Sex at birth. The 25.0 reference applies to men only. |
| height | Height | Your height without shoes. |
| weight | Weight | Your body weight. |
| bodyFat | Body fat | Your body fat as a percent of body weight, from a scan, calipers, or an estimate. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| normalized | Normalized FFMI | FFMI adjusted to a height of 1.80 m: FFMI + 6.3 × (1.80 − height in m) (Kouri et al. 1995). |
| ffmi | FFMI | Fat-free mass in kg ÷ height in m squared. |
| leanMass | Fat-free mass | Weight × (1 − body fat ÷ 100). |
| fatMass | Fat mass | Weight × body fat ÷ 100. |
| reference | Compared with Kouri et al. | For men: whether the normalized FFMI is within the 25.0 limit of steroid-free athletes in Kouri et al. (1995). |

## 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).

## Assumptions

- 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.

## Worked examples

1. sex = male, height = 1.778, weight = 81.646627, bodyFat = 15% gives ffmi = 21.952989, normalized = 22.091589, fatMass = 12.246994, reference = 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 = 1.65, weight = 60, bodyFat = 25% gives ffmi = 16.528926, normalized = 17.473926, leanMass = 45. Source: Kouri et al. (1995) definition: 60 × 0.75 = 45 kg.
3. sex = male, height = 1.8, weight = 90, bodyFat = 10% gives ffmi = 25, normalized = 25, reference = 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 = 1.7, weight = 95, bodyFat = 8% gives normalized = 30.872215, reference = Above the 25.0 limit of steroid-free athletes. Source: Kouri et al. (1995): 95 × 0.92 = 87.4 kg.

## FAQ

### 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.

## Sources

- Kouri EM, Pope HG Jr, Katz DL, Oliva P. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med. 1995;5(4):223-228. https://doi.org/10.1097/00042752-199510000-00003
- NIST SP 811 (2008), Appendix B: 1 lb = 0.45359237 kg and 1 in = 0.0254 m exactly.