FFMI Calculator

Name: FFMI Calculator
Author: CalculatorBolt

Calculate your Fat-Free Mass Index (FFMI) from weight, height, and body fat percentage. See interpretation categories for men and women, and use the target helper to estimate required lean mass for a desired FFMI. Informational only—consult health professionals. Explore more tools on free calculators on CalculatorBolt.

Calculator

Units

Total Body Weight (kg)

Your total body weight

Body Fat Percentage (%)

Percentage of body weight that is fat

Height (cm)

Your height in centimeters

Gender

Affects classification ranges

Age

Your age in years

Use Lean Mass Input

FFMI Rounding

FFMI

How it works

FFMI = Lean Mass / Height². Lean Mass = Weight × (1 − Body Fat%). We compute FFMI and map it to gender‑specific ranges (underfat, athletic, average, overfat).

Inputs explained

Gender: Male or Female - affects classification ranges.
Age: Your age in years (informational).
Height: Your height in cm or ft/in.
Weight: Your total body weight in kg or lbs.
Body Fat %: Percentage of body weight that is fat (measure with calipers, DEXA, or BIA).
Optional Lean Mass: Directly input lean mass instead of calculating from body fat.
Rounding: Number of decimal places for FFMI display.

Example

Male, 30 years, 175 cm, 75 kg, 20% body fat → Lean = 75×0.80=60 kg; Height²=3.0625 m² → FFMI = 60/3.0625 ≈ 19.6 → Category: Average

Tips & notes

FFMI is useful for assessing relative leanness regardless of overall weight.
Athletes may have higher FFMI due to greater muscle mass.
Always consider age, health status, and consult professionals for interpretation.

FFMI Classification Ranges

Classification	Male FFMI	Female FFMI
Underfat	< 16	< 15
Athletic	16–17	15–16
Average	17–20	16–19
Overfat	> 20	> 19

FAQs

For men, 17–20 is average; for women, 16–19. Athletes often have higher FFMI. "Underfat" ranges may indicate insufficient lean mass.

Use skinfold calipers, DEXA, BIA, or other methods. Enter the percentage here.

Yes. Athletes can use FFMI to track leanness; the athletic range is provided.

No. Everything runs in your browser. Use Export/Share Link to save your configuration.

FFMI is a measure of lean body mass (muscle, bone, organs) relative to height. It's calculated as Fat-Free Mass (kg) / Height (m)².

Build muscle through resistance training and adequate protein intake while maintaining or reducing body fat percentage.

Research suggests the natural upper limit for FFMI is around 25 for men and 22 for women, though individual variation exists.

Yes, enable the 'Use Lean Mass Input' option in Advanced Options to directly input your lean mass.

Disclaimer

Informational estimate only. FFMI is one metric and does not replace comprehensive health assessments. Consult qualified health and fitness professionals for advice.