Comprehensive Calculator Guide
The ponderal index (Rohrer’s index) divides your weight by your height cubed, not squared as BMI does. At 70 kg and 175 cm it is 13.1 kg/m³, with a BMI of 22.9. Dividing by the cube keeps tall people’s numbers from being pushed up, so it makes a useful second opinion for anyone well above or below average height.
Why the cube
Bodies are three-dimensional, so weight grows roughly with the cube of height. BMI therefore overstates tall people: at 198 cm and 95 kg, BMI is 24.2, near overweight, while the ponderal index is a mid-range 12.2.
A rough adult range is 11–15 kg/m³. The index is less established than BMI, so use it for comparison rather than diagnosis. Newborn charts use different units and limits.
How to Use
- Enter your weight.
- Enter your height, changing the unit if you like.
- Press “Calculate index” to see your ponderal index next to your BMI.
Formula Used
Ponderal index = weight (kg) ÷ height (m)³
Practical Examples
- Example 1
- 70 kg, 175 cm: 13.1 kg/m³; BMI 22.9.
- Example 2: tall
- 95 kg, 198 cm: 12.2 kg/m³; BMI 24.2.
Important Tips
- Above 190 cm or below 155 cm, compare both indexes before judging your weight.
Common Mistakes to Avoid
- Squaring the height instead of cubing it.
Frequently Asked Questions
- How do I calculate the ponderal index?
- Weight in kg divided by height in metres cubed.
- What is a normal ponderal index?
- Roughly 11–15 kg/m³ for adults.
- Is it better than BMI?
- It handles very tall and short people better, but BMI is the standard; use both.