FFMI Calculator
Fat-free mass index for athletes.
Private — runs in your browser Instant results
kg
cm
%
FFMI
19.7
Introduction
This result is an estimate based on the information provided. It is not a diagnosis and may not reflect individual medical circumstances.
What is FFMI Calculator?
Fat-free mass index (FFMI) relates estimated lean mass to height. It can be useful for tracking a personal estimate over time, but it is only as reliable as the body-fat percentage entered and does not measure health, performance, or eligibility for any treatment.
Definition: FFMI Calculator estimates fat-free mass index from body weight, height, and an estimated body-fat percentage.
Formula
FFMI = lean mass (kg) ÷ height (m)²; lean mass = body weight × (1 − body-fat percentage ÷ 100)
Calculation steps
- The core formula: FFMI = lean mass (kg) ÷ height (m)²; lean mass = body weight × (1 − body-fat percentage ÷ 100)
- Enter your values in the fields above — units and assumptions are under your control.
- The Daily Tools computes the result instantly in your browser using JavaScript.
- Review the result panel for the primary output and supporting breakdown values.
Worked example
Example: calculate FFMI from weight, height, and body fat
Inputs: Weight = 75 kg, Height = 180 cm, Body fat = 15%
- Estimate lean mass: 75 × (1 − 0.15) = 63.75 kg.
- Convert height to metres and square it: 1.80² = 3.24 m².
- Divide lean mass by height squared: 63.75 ÷ 3.24.
FFMI is about 19.7. It is an estimate because body-fat percentage is estimated.
Use cases
- Tracking an estimate using the same body-fat method over time
- Comparing lean-mass estimates relative to height
- Discussing training goals with a qualified coach or clinician
Advantages
- Browser-based processing — entered values and selected files are not sent to our servers
- No account required
- Instant results with a clean, readable interface
- Transparent formula shown on this page
Limitations
- Body-fat estimates can vary substantially by method and measurement conditions.
- This calculator displays unadjusted FFMI, not a diagnosis or a measure of athletic potential.
- Do not use the result to make medical, nutrition, or drug-use decisions.
Frequently asked questions
- What is the FFMI formula?
- The calculator estimates lean mass from weight and body-fat percentage, then divides it by height in metres squared.
- Is FFMI the same as BMI?
- No. BMI uses total body weight, while FFMI uses estimated lean mass.
- Why can FFMI change when my body-fat estimate changes?
- Body-fat percentage determines the estimated lean mass, so a different estimate changes the result.
- Is the FFMI Calculator free to use?
- Yes. FFMI Calculator on The Daily Tools is completely free, requires no account, and runs entirely in your browser.
- Does The Daily Tools store my inputs?
- No. Your numbers and text never leave your device. The Daily Tools has no backend database for calculator inputs.
- Who should use the FFMI Calculator?
- Anyone who needs a clear health and fitness calculation and wants to check the assumptions used.
- How accurate is the FFMI Calculator?
- Results follow the standard formula shown on this page. They are estimates for planning — not a substitute for professional medical advice.
- Can I use the FFMI Calculator on mobile?
- Yes. The Daily Tools is fully responsive and works on phones, tablets, and desktops.
Sources & references
Key points
- FFMI Calculator is a free, browser-based calculator for fat-free mass index for athletes.
- Formula: FFMI = lean mass (kg) ÷ height (m)²; lean mass = body weight × (1 − body-fat percentage ÷ 100)
- Private, browser-only processing
- Private, browser-based processing