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BMI Prime

Written by the HowToCalculateBMI.org team Updated 1 min read

Checked against 1 cited source Calculations checked by automated tests

BMI Prime is your BMI divided by 25, the BMI where the healthy range ends. A BMI Prime of 1.0 is exactly at that line, 0.90 is 10% below it, and 1.20 is 20% above it. A BMI of 22.5 has a BMI Prime of 22.5 ÷ 25 = 0.90. The calculator shows yours under the result.

BMI calculator

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Enter your height and weight to see your BMI and every step of the calculation.

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How to calculate BMI Prime

  1. Calculate your BMI as usual: weight (kg) ÷ height (m)², or 703 × lb ÷ in².
  2. Divide by 25.

BMI 22.5 ÷ 25 = 0.90

BMI 30 ÷ 25 = 1.20

BMI Prime chart

BMI BMI Prime Category
Below 18.5 Below 0.74 Underweight
18.5–24.9 0.74–0.99 Healthy weight
25–29.9 1.00–1.19 Overweight
30 and above 1.20 and above Obesity

Why use BMI Prime?

  • It reads as a percentage. 1.12 means 12% above the top of the healthy range, which can be easier to picture than "BMI 28".
  • It's easy to adjust. For guidelines that use a different upper limit, such as 23 for adults of Asian descent, divide by that limit instead. Asian BMI.

BMI Prime doesn't add new information: it's the same BMI on a different scale.

Frequently asked questions

What is a good BMI Prime?

0.74 to 0.99, the same as a BMI of 18.5 to 24.9.1

Is BMI Prime used by doctors?

Rarely. Doctors usually use BMI itself. BMI Prime is mostly a way to understand how far from the line you are.

Sources

  1. CDC ↩

Written by

The HowToCalculateBMI.org team

We explain BMI in plain language, check every worked example with automated tests, and keep each page up to date with current guidelines.

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Kept up to dateLast updated October 9, 2026
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This page is for education and is not medical advice. Talk with a healthcare professional about your weight and health.

What BMI Can and Can't Tell You BMI is a quick screening measure, but it can't tell muscle from fat or show where fat is stored. See who it misjudges and what to measure alongside… Read What Is BMI? BMI (body mass index) is your weight divided by your height squared. What it measures, what the number means, where it's used, and how to calculate… Read The History of BMI BMI began as the Quetelet index in the 1830s, was named body mass index by Ancel Keys in 1972, and became the standard weight measure in the 1990s… Read