FFMI Calculator (Fat-Free Mass Index)
Fat-free mass scaled to height² — the lifter's 'BMI for muscle', with the published natural reference bands.
Kouri's study of 157 athletes found steroid-free bodybuilders clustered under an FFMI of ~25 while steroid users routinely exceeded it — the origin of the famous 'natural limit'. It's a statistical ceiling from one cohort, not a law; female values run roughly 4–5 points lower.
Formula
For general information only — not medical or training advice. Estimates vary between individuals; consult a qualified professional before changing your exercise or nutrition routine.
Fat-free mass scaled to height² — the lifter's 'BMI for muscle', with the published natural reference bands. The FFMI Calculator (Fat-Free Mass Index) is a free, private ffmi tool — every result computes instantly in your browser with no sign-up and no data upload.
About FFMI Calculator (Fat-Free Mass Index)
Kouri's study of 157 athletes found steroid-free bodybuilders clustered under an FFMI of ~25 while steroid users routinely exceeded it — the origin of the famous 'natural limit'. It applies FFMI = FFM(kg) ÷ height²(m²). Use the FFMI Calculator (Fat-Free Mass Index) to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use FFMI Calculator (Fat-Free Mass Index)
- 1Enter your details in the FFMI Calculator (Fat-Free Mass Index) input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use FFMI Calculator (Fat-Free Mass Index)?
- ✓Instant ffmi result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Kouri EM et al., Clin J Sport Med 1995;5:223-8)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the FFMI Calculator (Fat-Free Mass Index) work?+
Kouri's study of 157 athletes found steroid-free bodybuilders clustered under an FFMI of ~25 while steroid users routinely exceeded it — the origin of the famous 'natural limit'. The calculation uses the formula: FFMI = FFM(kg) ÷ height²(m²). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the FFMI Calculator (Fat-Free Mass Index) accurate, and what is it based on?+
The method is traceable to authoritative sources: Kouri EM et al., Clin J Sport Med 1995;5:223-8. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the FFMI Calculator (Fat-Free Mass Index) free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is for general fitness information only, not medical or training advice. Consult a professional before changing your routine.
What can I use the FFMI Calculator (Fat-Free Mass Index) for?+
It's commonly used for ffmi, fat free mass index, ffmi calculator. Fat-free mass scaled to height² — the lifter's 'BMI for muscle', with the published natural reference bands.
Related Health tools
Adult BMI Calculator (WHO)
Body-mass index for adults with the WHO reference bands shown neutrally, plus the substituted formula step by step.
● LiveBMI Calculator (lb & inches)
US-style BMI from pounds and inches using the ×703 conversion, with CDC adult reference ranges.
● LiveBMI Calculator for Women
BMI with reference context written for women — what the index can and cannot say about female body composition.
● Live