---
type: WebApplication
title: "FFMI Calculator: Body Fat and Lean Mass"
description: "Type the numbers from an InBody, DEXA or scale printout and get body fat percentage, lean mass and normalized FFMI, with every step shown."
resource: https://quietgains.app/tools/ffmi-calculator
tags: ["ffmi", "body fat", "lean mass"]
timestamp: 2026-09-22
---

# What does my printout actually say?

Fat-free mass index (FFMI) is lean body mass in kilograms divided by height in metres squared, a measure of how much muscle you carry for your height. Three numbers off the sheet, plus sex for the ranges bar. Body fat, lean mass and normalized FFMI back, with every step shown.

## How the answer adds up.

Three lines of arithmetic most scan sheets do not print.

1. Body fat: 18.3 % (15.0 kg fat ÷ 82.0 kg × 100)
2. Lean mass: 67.0 kg (82.0 − 15.0 kg fat)
3. FFMI: 20.7 points (67.0 ÷ (1.80 m)² + 6.3 × (1.8 − 1.80), height adjusted)

Worked example: 82.0 kg with 15.0 kg of fat mass at 180 cm.

## Formula and sources

Body fat % = fat mass ÷ weight × 100.

Lean mass = weight − fat mass.

FFMI = lean mass ÷ height (m)². Normalized FFMI = FFMI + 6.3 × (1.8 − height (m)), which adjusts the index to a height of 1.80 m [1].

Ranges = the American Council on Exercise body fat ranges [3]. Men: under 6%, 6 to 13%, 14 to 17%, 18 to 24%, 25% and over. Women: under 14%, 14 to 20%, 21 to 24%, 25 to 31%, 32% and over. Each range takes one fifth of the bar.

1. 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. doi:10.1097/00042752-199510000-00003
2. Kyle UG, Bosaeus I, De Lorenzo AD, et al. "Bioelectrical impedance analysis, part II: utilization in clinical practice." Clin Nutr 2004;23(6):1430-1453. doi:10.1016/j.clnu.2004.09.012
3. American Council on Exercise. "Percent Body Fat Calculator": body fat percentage ranges for women and men. acefitness.org.

## Reading the result

### What the FFMI study found

Kouri et al. (1995) measured 157 male athletes. The normalized FFMI of the 74 who had not used anabolic steroids reached up to 25.0.

### Devices differ

Bioimpedance scales, DEXA and calipers measure fat mass in different ways, so their numbers are not interchangeable (Kyle et al., 2004).

### Same conditions each time

Bioimpedance guidance measures after fasting, with an empty bladder and without recent exercise, because each of these shifts the reading (Kyle et al., 2004).

## Related

- [Macros](https://quietgains.app/tools/macro-calculator)
- [Water intake](https://quietgains.app/tools/water-intake-calculator)
- [Reading an InBody printout](https://quietgains.app/journal/reading-an-inbody-printout)
- [Every free tool](https://quietgains.app/tools)

Photograph the sheet instead. QuietGains reads the numbers from a photo of your InBody sheet and keeps every test in one history. Arithmetic only. Not medical advice.