Body Roundness Index
The index treats the body as an ellipse and measures how flattened it is. It captures the belly that BMI misses, so two people with the same BMI differ once their waists do. Values usually land between 1 and 16.
Your numbers
Body roundness index
3.36
Waist-height ratio
0.5
Formula
Body roundness index = 364.2 − 365.5 × √(1 − ((Waist (cm) ÷ 2π) ÷ (0.5 × Height (cm)))²)
It ignores weight, so it cannot tell muscle from fat. Read it next to BMI and the waist measurement itself.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Height (cm) (cm)Height in centimetres; converted to metres inside the formula. | 170 | 0 and up |
| Waist (cm) (cm)Waist at navel height, measured after breathing out. | 85 | 0 and up |
Step by step
Quick reference table
Results when only Height (cm) (cm) changes and everything else stays put.
| Height (cm) (cm) | Body roundness index | Waist-height ratio |
|---|---|---|
| 85 | 17.71 | 1 |
| 128 | 6.96 | 0.664 |
| 170 | 3.36 | 0.5 |
| 255 | 0.76 | 0.333 |
| 340 | 0 | 0.25 |
What each result means
| Result | At default values |
|---|---|
| Body roundness index | 3.36 |
| Waist-height ratioWaist over height; the line people watch is 0.5. | 0.5 |
Common mistakes
It ignores weight, so it cannot tell muscle from fat. Read it next to BMI and the waist measurement itself.
Glossary
- Height (cm)
- Height in centimetres; converted to metres inside the formula.
- Waist (cm)
- Waist at navel height, measured after breathing out.
- Waist-height ratio
- Waist over height; the line people watch is 0.5.
Frequently asked questions
Q. How is Body Roundness Index calculated?
Body roundness index = 364.2 − 365.5 × √(1 − ((Waist (cm) ÷ 2π) ÷ (0.5 × Height (cm)))²) — The index treats the body as an ellipse and measures how flattened it is. It captures the belly that BMI misses, so two people with the same BMI differ once their waists do. Values usually land between 1 and 16.
Q. Can you walk through an example?
With Height (cm) 170cm, Waist (cm) 85cm, the answer is Body roundness index 3.36.
Q. What do I need to enter?
Enter Height (cm), Waist (cm). The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Height (cm) (cm) moves the answer to Height (cm) (cm) 85 → Body roundness index 17.71 and Height (cm) (cm) 340 → Body roundness index 0. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
It ignores weight, so it cannot tell muscle from fat. Read it next to BMI and the waist measurement itself.
Related calculators
These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.