FFMI calculator
Fat-free mass index measures how much lean mass you carry for your height. Unlike BMI it ignores fat entirely, which makes it the more useful number for anyone who lifts. Both the raw and the height-normalised figure are shown.
You need a body fat percentage for this. If you do not have one, estimate it first with the body fat calculator.
- Raw FFMI
- 21.5
- Fat-free mass
- 68 kg
- Band
- Above average
An estimate from a published formula, not a measurement. Use it as a consistent yardstick for tracking change.
Reading the bands
Bands differ by sex because average lean mass does. They describe populations, not individuals, and say nothing about how strong someone is.
| Band | Normalised FFMI | What it usually reflects |
|---|---|---|
| Below average | < 18 | Little resistance training, or a long layoff |
| Average | 18-20 | Typical for an untrained adult |
| Above average | 20-22 | A year or two of consistent lifting |
| Well muscled | 22-25 | Years of consistent training |
| Exceptional | 25+ | Rare, and often the upper end of the discussion below |
How it is calculated
Fat-free mass divided by height in metres squared. It is BMI with the fat removed, which is exactly the correction BMI needs before it can say anything useful about a lifter.
The normalised figure adds a height adjustment of 6.1 times the difference between your height and 1.8 metres. Without it, tall people score lower for the same build, because lean mass does not scale with the square of height quite the way the raw index assumes.
The 25 ceiling, and what the study actually said
A 1995 paper by Kouri and colleagues measured a group of bodybuilders and found that drug-free lifters clustered below a normalised FFMI of around 25, while users sat above it. That single finding became an internet rule for detecting steroid use.
It does not hold as a rule. The sample was small, it was one population, and outliers on both sides are documented. A normalised FFMI above 25 is uncommon and is not evidence of anything on its own. Treating it as proof is a misreading of the paper.
Where the error comes from
Almost all of it comes from the body fat input. Height and weight are easy to measure accurately; body fat is not. A two-point error in body fat moves FFMI by roughly half a point, so a figure from a bathroom scale can produce a confidently wrong index.
This is why the raw and normalised numbers are shown together. If they are being compared to anything, it should be your own earlier figures taken with the same body fat method.
What it does not measure
FFMI counts lean tissue, and lean tissue includes bone, organs and water as well as muscle. It also says nothing about distribution, and nothing whatsoever about strength. A powerlifter and a physique competitor can share an FFMI and share almost no training outcome.
Questions people ask
What is a good FFMI?
For men, around 20 to 22 reflects a couple of years of consistent training and 22 to 25 reflects years of it. For women the equivalent bands sit roughly 4 points lower. Above those ranges is uncommon rather than impossible.
Is FFMI better than BMI?
For anyone with meaningful muscle mass, yes. BMI classifies a lean 100 kg lifter as obese because it cannot separate muscle from fat. FFMI removes fat from the equation entirely, which is the whole point of it.
Does an FFMI over 25 prove steroid use?
No. It comes from one small 1995 study and was never a diagnostic threshold. Genuine outliers exist, and the number is only as good as the body fat estimate behind it, which is usually the least reliable input.
Why is there a height adjustment?
Because the raw index divides by height squared, which under-credits tall people. The normalisation restates everyone at a 1.8 m reference so two lifters of different heights and the same build get comparable numbers.
Related tools
Lean mass is built one session at a time
Mekimeki keeps the record that matters: what you lifted, for how many, and whether it is more than last time.
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