Three signals are better than one
Body Composition Calculator
Compare BMI, waist-to-height ratio and a waist-based body-fat estimate in one place. None is a diagnosis, but the pattern is more informative than BMI alone.
Metric or US unitsBMI categoryWaist-to-height ratioRelative fat mass estimate
Enter your information
Enter comparable measurements
Measure waist consistently at the midpoint between the lowest rib and top of the hip bone, after a normal exhale.
RFM uses sex-specific coefficients from the published equation. If neither equation is appropriate for you, use the BMI and waist-to-height results and leave the body-fat estimate as a rough research comparison.
Calculated result
Your measurement pattern
Waist-to-height ratio0.48Below the 0.50 central-adiposity threshold
BMI24.7
BMI categoryHealthy-weight range
Estimated RFM22.1%
The three measurements broadly agree. Track the trend under the same measuring conditions.
Waist ratio: 86 cm ÷ 180 cm = 0.478
How to use the answer
Read the pattern rather than chasing one category
BMI reflects weight relative to height, waist-to-height ratio adds central adiposity, and RFM estimates whole-body fat from height and waist. Each can be wrong in a different way.
BMI
Weight ÷ height²Fast and widely studied, but it cannot distinguish fat, muscle, bone or fat distribution.
Waist-to-height
Under 0.50NICE recommends keeping waist below half of height; 0.50–0.59 indicates increased central adiposity.
Relative fat mass
Waist-based estimateRFM outperformed BMI against DXA in its development datasets, but an individual estimate can still be several points off.
Important limitations
What the number can—and cannot—tell you
Can this diagnose obesity or health risk?+
No. Current expert frameworks increasingly combine excess-fat measures with symptoms, function and health complications. A calculator cannot establish those.
Why might a muscular person have a high BMI?+
BMI counts all body mass. High lean mass can raise BMI without the same body-fat pattern, which is why waist and clinical context help.
How should I track change?+
Use the same tape location, posture, time of day and unit. Small day-to-day circumference changes can be measurement noise.