How to Calculate Your BMI
Step-by-step BMI calculation in metric and imperial units, with a quick interpretation of the result.
Reviewed Jan 15, 2025
Quick answer
Divide your weight in kilograms by your height in meters squared. For imperial, use 703 × weight (lb) ÷ height (in)². A healthy BMI for adults is 18.5–24.9.
Try it
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Find your Body Mass Index and see where it sits on the standard healthy-range scale.
Result
Fill in the inputs to see your result.
Inputs
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How it works
BMI is a screening tool that estimates whether your weight is in a healthy range relative to your height. It doesn't measure body fat directly.
Formula
BMI = weight (kg) ÷ height (m)²
Common mistakes
- Mixing units — entering height in cm but weight in pounds.
- Treating BMI as a diagnosis. It's a screening signal, not a verdict.
- Using adult ranges for children or teens.
- Ignoring muscle mass — athletes often score 'overweight' but have low body fat.
Source & methodology
Healthy ranges follow WHO adult cut-offs: underweight <18.5, healthy 18.5–24.9, overweight 25–29.9, obese ≥30.
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Step by step (metric)
Measure your height in cm
Then divide by 100 to get meters.
Square your height
Multiply meters × meters.
Divide weight by that
BMI = kg ÷ m²