FFMI Calculator: Find Your Fat-Free Mass Index
See your fat-free mass index and how it compares to typical lifters, plus a normalized score that adjusts for height.
TL;DR
FFMI (fat-free mass index) measures muscle mass relative to height: divide your lean body mass in kilograms by your height in meters squared. This FFMI calculator also shows your normalized FFMI, adjusted to a 1.80 m height, so lifters of different heights compare fairly, plus how your number stacks up against population percentiles.
FFMI
22.6
In the top 5% for your sex.
Normalized FFMI
22.7
Lean mass
157.3 lb
Fat mass
27.7 lb
Normalized FFMI adjusts your score to a 1.80 m (5'11") height, so lifters of different heights compare fairly.
Where you land
Median (18.9)
Top 5% (21.1)
Natural limit (25)
Track Your Body Composition Over Time
PR Streak tracks your body weight, body fat and 11 body measurements with charts, and catches every personal record automatically as your training builds lean mass.
What Is FFMI?
FFMI stands for fat-free mass index. It measures how much muscle, or fat-free mass, you carry relative to your height, so two lifters at very different heights can be compared on the same scale.
It's a more useful number than body weight alone for judging muscularity, since a taller lifter naturally carries more lean mass at the same leanness.
How This FFMI Calculator Works
Enter your height, weight and body fat percentage. The calculator first finds your lean mass: weight x (1 - body fat % / 100). FFMI is then your lean mass in kilograms divided by your height in meters squared.
Normalized FFMI adjusts that score to a 1.80 m (5'11") height: normalized FFMI = FFMI + 6.1 x (1.8 - height in meters). The source paper's abstract prints 6.3, but its actual formula, and the one calculators including this one use, is 6.1.
If you don't know your body fat percentage, estimate it right in this calculator with the U.S. Navy tape method, or get the full breakdown on the body fat calculator.
FFMI is only as accurate as the body fat percentage that goes into it. A rough body fat estimate produces a rough FFMI, so use your best measurement.
What Is a Good FFMI?
In a study of 5,635 healthy Swiss adults, men aged 18 to 34 had a median FFMI of 18.9, with the middle 90% falling between 16.8 and 21.1. Women aged 18 to 34 had a median of 15.4, with the middle 90% between 13.8 and 17.6.
FFMI percentiles for men, by age (Schutz et al. 2002)
| Age | 5th | 10th | 25th | 50th | 75th | 90th | 95th |
|---|---|---|---|---|---|---|---|
| 18-34 | 16.8 | 17.2 | 18.0 | 18.9 | 19.8 | 20.5 | 21.1 |
| 35-54 | 17.2 | 17.6 | 18.3 | 19.2 | 20.1 | 21.1 | 21.7 |
| 55-74 | 17.0 | 17.6 | 18.4 | 19.4 | 20.3 | 21.1 | 22.1 |
| 75+ | 16.6 | 16.9 | 17.6 | 18.5 | 19.4 | 20.9 | 21.2 |
FFMI percentiles for women, by age (Schutz et al. 2002)
| Age | 5th | 10th | 25th | 50th | 75th | 90th | 95th |
|---|---|---|---|---|---|---|---|
| 18-34 | 13.8 | 14.1 | 14.7 | 15.4 | 16.2 | 17.1 | 17.6 |
| 35-54 | 14.4 | 14.7 | 15.3 | 15.9 | 16.7 | 17.5 | 18.0 |
| 55-74 | 14.1 | 14.6 | 15.4 | 16.2 | 17.4 | 18.4 | 19.0 |
| 75+ | 12.9 | 13.7 | 14.7 | 15.9 | 17.0 | 18.1 | 18.7 |
An FFMI above the median for your age and sex puts you ahead of half the general population; above the 95th percentile puts you in the top 5%. For more on typical muscle gain over time, see our muscle-building statistics.
Lean Mass Needed for a Target FFMI
How much lean mass a given FFMI takes depends on height: a taller lifter needs more lean mass to reach the same score. Here's the lean mass needed for FFMI 20, 22, 24 and 25 at common heights.
Lean mass needed for a target FFMI, by height
| Height | Lean mass at FFMI 20 | Lean mass at FFMI 22 | Lean mass at FFMI 24 | Lean mass at FFMI 25 |
|---|---|---|---|---|
| 5'4" (163 cm) | 117 lb (53 kg) | 128 lb (58 kg) | 140 lb (63 kg) | 146 lb (66 kg) |
| 5'6" (168 cm) | 124 lb (56 kg) | 136 lb (62 kg) | 149 lb (67 kg) | 155 lb (70 kg) |
| 5'8" (173 cm) | 132 lb (60 kg) | 145 lb (66 kg) | 158 lb (72 kg) | 164 lb (75 kg) |
| 5'10" (178 cm) | 139 lb (63 kg) | 153 lb (70 kg) | 167 lb (76 kg) | 174 lb (79 kg) |
| 6'0" (183 cm) | 147 lb (67 kg) | 162 lb (74 kg) | 177 lb (80 kg) | 184 lb (84 kg) |
| 6'2" (188 cm) | 156 lb (71 kg) | 171 lb (78 kg) | 187 lb (85 kg) | 195 lb (88 kg) |
| 6'4" (193 cm) | 164 lb (75 kg) | 181 lb (82 kg) | 197 lb (89 kg) | 205 lb (93 kg) |
For a more personal number, see how much of your own weight is lean mass with the lean body mass calculator.
Is FFMI 25 the Natural Limit? (Natty or Not)
A widely cited 1995 study compared 157 male athletes, 83 steroid users and 74 nonusers. Among the drug-free men, normalized FFMI "extended up to a well-defined limit of 25.0"; many steroid users easily exceeded 25, and some exceeded 30.
That makes 25 a useful reference point, not a verdict on any one person. Genetics, years of consistent training, measurement error and how lean you are on the day you measure can all push a natural lifter's FFMI close to or above that ceiling. Treat it as context for where drug-free men in that study topped out, not a test.
How Accurate Is FFMI?
FFMI is only as accurate as the body fat percentage you enter. A tape-measurement estimate is close enough for tracking trends, but it will shift your FFMI up or down along with any error in that number.
Track your FFMI's trend over time rather than judging a single reading, since consistent measurement technique matters more than any one data point.
Used by lifters following PPL, 5x5, upper/lower, and more.
Frequently Asked Questions
What is FFMI?
FFMI (fat-free mass index) measures your muscle mass relative to your height: it's your lean body mass in kilograms divided by your height in meters squared. It lets lifters of different heights compare muscularity on the same scale.
What is a good FFMI?
For men aged 18 to 34, the population median FFMI is 18.9, with the top 5% above 21.1. For women in that age range, the median is 15.4, with the top 5% above 17.6. Anything above the median for your age and sex is above average.
Is an FFMI of 25 the natural limit?
A 1995 study found that drug-free male athletes' normalized FFMI "extended up to a well-defined limit of 25.0," while many steroid users easily exceeded it. It's a useful reference point from that specific study, not proof about any individual lifter.
How do I calculate FFMI without a body fat scale?
Estimate your body fat percentage with the U.S. Navy tape method (neck, waist and, for women, hip measurements). This calculator can do that for you, then it converts the estimate straight into your FFMI and normalized FFMI.
What is normalized FFMI?
Normalized FFMI adjusts your raw FFMI to a 1.80 m (5'11") height, using the formula FFMI + 6.1 x (1.8 - height in meters). It's the fairer number for comparing lifters of different heights.
Does FFMI work for women?
Yes. The formula is the same for both sexes; only the reference percentiles differ. Women aged 18 to 34 have a population median FFMI of 15.4, versus 18.9 for men in the same age range.
How accurate is FFMI?
FFMI is only as accurate as the body fat percentage used to calculate it. A tape-measurement estimate is good enough to track trends over time, but any error in that number shifts your FFMI by roughly the same amount.
Sources
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