What is BMI Prime and how is it calculated?

BMI Prime is a dimensionless ratio: BMI Prime = BMI ÷ 25, where 25 kg/m² is the upper limit of the WHO healthy-weight range. A value of 1.00 means you are exactly at the ceiling, 1.20 means 20% above it, and 0.80 means 20% below it. Categories: under 0.74 underweight, 0.74–0.99 healthy, 1.00–1.19 overweight, 1.20 and over obese.

How accurate is BMI Prime?

BMI Prime is exactly as accurate as BMI — it is the same measurement on a different scale. Like all BMI-based measures it is a screening tool and does not distinguish muscle from fat or account for body composition, age or ethnicity, so it should not be used alone to assess health.

Yes. Your height and weight are used only inside your browser to compute the result. Nothing is stored or transmitted anywhere.

BMI Prime Calculator

BMI Prime calculator

BMI Prime rescales your body mass index so the healthy-weight ceiling becomes an easy-to-read 1.00. It is simply your BMI divided by 25:

BMI Prime = BMI ÷ 25

A BMI Prime of 1.00 means you sit exactly at the top of the healthy range. 1.20 means you are 20% above it; 0.80 means 20% below. That makes it intuitive to see at a glance how far you are from the healthy ceiling.

Enter your height and weight in metric or imperial and the tool shows your BMI, your BMI Prime, the category and the percentage above or below the healthy limit.

Like all BMI-based measures, BMI Prime is a screening tool only — it does not account for muscle mass or body composition. All maths runs locally in your browser and your measurements never leave your device.