Question 1

What is BMI Prime?

Accepted Answer

BMI Prime is the ratio of your actual BMI to the upper limit of normal BMI (25). A BMI Prime of 0.74 means you're at 74% of the overweight threshold; 1.0 means you're exactly at the threshold; 1.2 means you're 20% over it. It's a simpler, more intuitive way to express BMI.

Question 2

What's the difference between BMI and BMI Prime?

Accepted Answer

BMI is the raw number (e.g. 28.5 kg/m²). BMI Prime divides BMI by 25 to show how far above or below the 'normal' cutoff you are. BMI Prime makes it easier to compare across different heights and to track small changes over time.

Question 3

Is BMI Prime more accurate than BMI?

Accepted Answer

Not necessarily more accurate, but easier to interpret. Both BMI and BMI Prime are screening tools that don't directly measure body fat. Athletes and very muscular people can have high BMI without being unhealthy. Use BMI Prime alongside waist-to-height ratio for a fuller picture.

Question 4

What is the Ponderal Index?

Accepted Answer

The Ponderal Index (PI) is similar to BMI but uses height cubed instead of squared: weight / height³. It's preferred for very tall or very short people because it reduces the bias BMI has at the extremes of height.