Fat-free mass index from your weight, height and body fat: the raw and the height-normalized FFMI, set against the published low, median and natural-limit markers for men and women.
FFMI Calculator - Fat-Free Mass Index, Normalized
Fat-free mass index from your weight, height and body fat: the raw and the height-normalized FFMI, set against the published low, median and natural-limit markers for men and women.
Parameters
Enter data for calculations
💡 Fill in all required fields to unlock the calculate button
FFMI: lean mass for your height, with the fat left out
A 5'10" man at 180 lb and 15% body fat carries 153.0 lb of fat-free mass, a fat-free mass index of 22.1. Cut to 170 lb at 10% and his FFMI is still 22.1; add 8.5 lb of lean mass instead and it climbs to 23.3. That is what FFMI measures: fat-free mass scaled to height, so it ignores fat and rewards muscle. This FFMI calculator returns the raw and the height-normalized index and places it next to the published markers: the clinical low cut-off, the population median and, for men, the 25.0 limit from the study that introduced the index.
Four entries for an FFMI
- Sex - sets which reference values the result shows.
- Body weight - in pounds or kilograms, decimals allowed.
- Height - feet and inches, or centimeters.
- Body fat percentage - from a DEXA scan, calipers, a bioimpedance scale or the Navy tape method. This number decides the accuracy of everything else.
The formula and the 6.3 correction
Fat-free mass is weight minus fat: weight x (1 - body fat / 100). The raw index divides it by height in meters squared, exactly like BMI does with weight. Kouri and colleagues, who introduced FFMI in a study of 157 male athletes, then added a small correction to compare everyone with a 1.80 m man:
Many calculators print 6.1 instead of the 6.3 in the paper; at 5'5" the gap is 0.03 points.
Before and after: a cut, a lean bulk, a wrong reading
Same 5'10" man, three changes.
| Situation | Weight | Body fat | Fat-free mass | FFMI |
|---|---|---|---|---|
| Before | 180 lb | 15% | 153.0 lb | 22.1 |
| After a cut | 170 lb | 10% | 153.0 lb | 22.1 |
| After a lean bulk | 190 lb | 15% | 161.5 lb | 23.3 |
| Before, scale reads 12% instead of 15% | 180 lb | 12% | 158.4 lb | 22.9 |
The last row is why the result shows a range: three points of body fat move FFMI by 0.8, as much as 5.4 lb of real fat-free mass would. Before the lean bulk the man was 20.3 lb of fat-free mass short of 25.0; after it, 11.8 lb.
Fat-free mass behind each FFMI, by height
Pounds of fat-free mass a man needs for a normalized FFMI of 20, 22, 24 and 25, with the 6.3 correction.
| Height | FFMI 20 | FFMI 22 | FFMI 24 | FFMI 25 |
|---|---|---|---|---|
| 5'6" | 119.1 lb | 131.5 lb | 143.9 lb | 150.1 lb |
| 5'8" | 128.5 lb | 141.7 lb | 154.8 lb | 161.4 lb |
| 5'10" | 138.4 lb | 152.4 lb | 166.3 lb | 173.3 lb |
| 6'0" | 148.8 lb | 163.6 lb | 178.3 lb | 185.7 lb |
| 6'2" | 159.7 lb | 175.3 lb | 190.8 lb | 198.6 lb |
| 6'4" | 171.1 lb | 187.5 lb | 203.9 lb | 212.1 lb |
What a good FFMI is, by the published numbers
There is no official grading scale, so the result shows four figures from research instead:
- Low: below 17 for men, below 15 for women. The ESPEN consensus on diagnosing malnutrition uses these cut-offs, together with unintended weight loss.
- Median: 18.9 for men, 15.4 for women aged 18 to 34, from 5,635 Swiss adults measured by bioimpedance (Schutz and colleagues). These two and the low cut-offs are raw FFMI, so the result compares them with your raw number.
- 25.0 for men. In Kouri's sample, normalized FFMI of athletes who had never used steroids "extended up to a well-defined limit of 25.0", while many steroid users passed it and some went over 30.
- 25.4 for men. The estimated mean of 20 Mr. America winners from the pre-steroid era.
Two cautions. Kouri measured men only, so the often-quoted "22 for women" has no study behind it. And the authors called the 25.0 finding preliminary, a screening idea, not a rule.
FFMI questions with numbers
Related tools
Intermittent Fasting Calculator
Eating window, meal times and the next opening for 14:10, 16:8, 18:6, 20:4, OMAD and 5:2 - See the calculator
Steps to Miles Calculator
Steps to miles and km by height, or a distance to steps, with walking time and calories - See the calculator
Body Fat Calculator
Body fat percentage from tape measurements with the U.S. Navy method - See the calculator
BMI Calculator
Body mass index and the weight range for your height - See the calculator
Protein Intake Calculator
Daily protein by body weight, activity and goal - See the calculator
Calorie Surplus Calculator
Calories for a lean bulk at a chosen rate of gain - See the calculator
One Rep Max Calculator
Your one-rep max from a set of several reps - See the calculator