Fat-Free Mass Calculator (FFMI)
Enter your weight, height and body fat percentage to get your fat-free mass and fat-free mass index (FFMI), a height-adjusted measure of how muscular you are. It's a more useful number than BMI for people who lift weights.
Fat-Free Mass (FFM) represents all body mass except adipose tissue: muscle, bone, organs, connective tissue, and water. FFMI scales lean mass to height squared (kg/m²), providing an objective indicator of muscular development independent of body fat.
Fat-Free Mass (FFM)
Above AverageRaw FFMI: 21 · Normalized FFMI: 21. Solid muscular development consistent with regular resistance training.
FFMI Natural Muscularity Standards (Men)
| Classification | Men FFMI | Women FFMI |
|---|---|---|
| Below Average | < 18.0 | < 15.0 |
| Average | 18.0 – 19.9 | 15.0 – 16.9 |
| Above Average | 20.0 – 21.9 | 17.0 – 18.9 |
| Excellent | 22.0 – 22.9 | 19.0 – 19.9 |
| Superior / Natural Limit | 23.0 – 25.0 | 20.0 – 22.0 |
| Exceptional Genetics / Elite | > 25.0 | > 22.0 |
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Clinical Equations
WHO, CDC, ACSM & Mifflin-St Jeor
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How to use Fat-Free Mass Calculator
- 1Enter your body weight and measured body fat percentage.
- 2Enter your height in cm or feet and inches.
- 3View your Fat-Free Mass (kg/lb), raw FFMI, and height-normalized FFMI score.
Understanding FFMI and natural muscularity
While BMI groups muscle and fat together, FFMI isolates your muscular framework. An FFMI of 18–20 represents average muscularity for men, 20–22 indicates dedicated training, and 22–25 represents elite natural physique development.
Normalized FFMI adjusts for height disparities based on the classic 1.80m benchmark (Normalized FFMI = FFMI + 6.1 × (1.8 - height in meters)).
Frequently Asked Questions
What is a good FFMI?
For men, 18 to 20 is typical, 20 to 22 above average, and 22 to 25 very muscular. Women's values are usually about 3 points lower.
What is the natural FFMI limit?
A widely cited study of male athletes found few natural lifters above about 25. It's a guide, not a hard rule.
Is fat-free mass the same as lean body mass?
They're nearly the same; in everyday use the terms are interchangeable.
Related Calculators
Lean Body Mass Calculator
Calculate your lean body mass from height and weight using Boer, James, and Hume formulas or body fat %.
Body Fat Calculator
Estimate your body fat percentage using the US Navy tape method or Deurenberg BMI equation.
BMI Calculator
Calculate your Body Mass Index in metric or imperial, with CDC youth LMS percentiles and Asian cut-offs.
Body Recomposition Calculator
Plan a body recomposition: calories, protein, and timeline to lose fat while gaining muscle.
Strength-to-Weight Ratio Calculator
Calculate your strength-to-bodyweight ratio for bench, squat, deadlift or pull-ups.
Scientific Sources & Evidence
- World Health Organization (WHO) — Body Mass Index Classification
- CDC Growth Charts — BMI-for-age LMS Percentiles
- Mifflin et al. (1990) — Basal Metabolic Rate Predictive Equations
- NICE Guideline NG246 — Identification and Management of Overweight and Obesity
- American College of Sports Medicine (ACSM) — Exercise Testing & Prescription
- European Food Safety Authority (EFSA) — Dietary Reference Values for Water