FFMI Calculator
Use this FFMI calculator to estimate how much of your bodyweight is fat-free mass and compare that amount with your height. Enter your bodyweight, height and best current body-fat estimate.
Because body-fat measurements are estimates, even a small change can move your FFMI. Record the method you used so future results are easier to compare; the height adjustment comes from a study of male athletes and is not a natural-limit or drug-use test.
You’ll get fat-free mass, FFMI, height-adjusted FFMI and a personalized body-fat comparison chart. Save your result to keep the measurements and method together for your next check.
What Your FFMI Result Means
Your FFMI compares estimated fat-free mass with your height. Read it beside the body-fat percentage and measurement method you entered, because a different body-fat estimate can change the answer even when bodyweight and height stay the same.
The result card names the Kouri, Pope, Katz and Oliva method, then shows estimated fat-free mass and height-adjusted FFMI. Save the measurements and body-fat method together when you want to compare another check later.
Calculate above to see your result and the measurements behind it.
Use Measurements You Can Repeat
Enter your current bodyweight, standing height and best available body-fat estimate. Body-composition scales, waist equations, skinfolds and scans can give different percentages, so use the same method when you compare changes.
The body-fat comparison range is optional. It lets you see what happens if the estimate is a little higher or lower; it is not a personal error bar or confidence interval.
- Bodyweight unit
- Choose the unit used for your bodyweight.
- Height unit
- Choose the unit used for your standing height.
- Bodyweight
- Enter your current bodyweight in the unit selected above.
- Height
- Enter your standing height without shoes.
- Estimated body fat
- Enter your body-fat percentage. Use the same measurement method when comparing results.
- Body-fat comparison range
- Choose how many percentage points above and below your estimate to compare. This shows sensitivity, not a measured error margin.
- How was body fat estimated?
- Record the method behind the percentage you entered, so you can compare like-for-like measurements later. This label does not change the calculation.
How Body-Fat Estimates Change Your FFMI
The chart holds bodyweight and height constant while changing only the body-fat estimate. It answers a practical question: how much would your FFMI move if that one input were different?
Use the highlighted entered value as your result. The nearby values are scenarios, and the complete table gives every plotted number without relying on color.
Vertical axis: FFMI (kg/m²)
On a small screen, swipe the graph sideways or open its data table.
Horizontal axis: Assumed body fat (%)
- FFMI sensitivity
View all chart values and details
| Body fat | Fat-free mass | Raw FFMI | Height-adjusted FFMI | Scenario status |
|---|---|---|---|---|
| 13% | 153.44 lb | 21.48 kg/m² | 21.48 kg/m² | Scenario |
| 14% | 151.68 lb | 21.23 kg/m² | 21.23 kg/m² | Scenario |
| 15% | 149.91 lb | 20.99 kg/m² | 20.99 kg/m² | Your entered estimate |
| 16% | 148.15 lb | 20.74 kg/m² | 20.74 kg/m² | Scenario |
| 17% | 146.39 lb | 20.49 kg/m² | 20.49 kg/m² | Scenario |
Where the FFMI Method Comes From
FFMI was introduced in a 1995 study of 157 male athletes: 74 who reported no anabolic-steroid use and 83 who reported use. The height adjustment on this page comes from that specific sample.
That study explains the calculation; it does not turn one result into a universal ranking. This calculator therefore shows your arithmetic and measurement sensitivity without labeling you natural, enhanced, healthy, good or elite.
How FFMI Is Calculated
First, the calculator estimates fat-free mass: bodyweight × (1 − body-fat percentage ÷ 100). FFMI is fat-free mass in kilograms divided by height in meters squared.
Height-adjusted FFMI adds 6.3 × (1.8 − height in meters) to raw FFMI. Keep the raw and adjusted values separate because only the second uses that source-specific height adjustment.
See the equations and calculation details
| Result | How it is calculated |
|---|---|
| Estimated fat-free mass | Bodyweight × (1 − body-fat percentage ÷ 100) |
| FFMI | Fat-free mass in kilograms ÷ height in meters squared |
| Height-adjusted FFMI | FFMI + 6.3 × (1.80 − height in meters) |
A Complete FFMI Example
Choose Use example to try these inputs, then enter your own values.
Changing bodyweight units preserves FFMI; fat-free mass uses your selected weight unit. FFMI stays in kg/m².
| Result | Value |
|---|---|
| Bodyweight unit | lb |
| Height unit | in |
| Bodyweight | 176.37 lb |
| Height | 70.87 in |
| Estimated body fat (%) | 15 |
| Body-fat comparison range | 2 |
| How did you estimate body fat? | Not recorded |
| FFMI | 20.99 kg/m² |
| Fat-free mass | 149.91 lb |
| Height-adjusted FFMI | 20.99 kg/m² |
What FFMI Can and Cannot Tell You
FFMI includes all estimated fat-free tissue, including water, bone and organs; it is not a direct muscle-mass measurement. Hydration, body-fat method and measurement conditions can change the result.
The height-normalization study included 157 male athletes, including steroid users and nonusers. It does not provide a universal percentile, a diagnosis, a personal natural limit or proof of drug use.
- Fat-free mass index in users and nonusers of anabolic-androgenic steroids — Kouri, Pope, Katz and Oliva (1995).
- Guide for the Use of the International System of Units (SI) — NIST (2008).