BMI Prime Calculator

BMI as a ratio of the upper healthy limit. Free, private and instant.

How to use the BMI Prime

  1. Pick metric (cm, kg) or imperial (ft, in, lb) units.
  2. Choose reference standard: WHO / international or Asian-Pacific (South Asian).
  3. Enter height.
  4. Enter weight.
  5. Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.

About the BMI Prime

BMI Prime divides your BMI by the upper limit of the healthy range. A value below 1.0 is within the limit, and a value above 1.0 shows by what percentage you exceed it.

Also known as: BMI prime, BMI ratio calculator, BMI prime index.

Worked example

BMI Prime: 0.97 (Healthy). Your BMI of 24.2 is 3% below the upper healthy limit of 25.

Formula and cut-offs

BMI Prime = BMI / 25 (WHO) or BMI / 23 (Asian-Pacific). Under 0.74 underweight, 0.74-0.99 healthy, 1.0-1.19 overweight, 1.2 and above obese.

Frequently asked questions

What does a BMI Prime of 1.2 mean?

Your BMI is 20% above the upper healthy limit of 25, which corresponds to a BMI of 30.

Why use BMI Prime?

It is a unit-free ratio that makes it easy to see how far you are from the limit and to compare across different BMI cut-offs.

How do I calculate BMI Prime?

Divide your BMI by the upper limit of the healthy range. With WHO cut-offs that is BMI / 25, so a BMI of 27.5 gives a BMI Prime of 1.1, or 10% above the upper healthy limit.

What is the BMI prime for 170 cm and 70 kg?

BMI Prime: 0.97 (Healthy). Your BMI of 24.2 is 3% below the upper healthy limit of 25. Enter your own numbers above for a personal result.

Sources and references

Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.

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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.