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BMI Calculator

Body Mass Index with the WHO weight category and a clear visual scale.

Choose imperial or metric, then enter your height and weight. Your BMI and category appear instantly.

Your BMI
24.4
Normal weight
< 18.518.5–24.925–29.9≥ 30

Body Mass Index (BMI) is a quick screening number that relates weight to height. It is not a body-fat measurement, but it is a widely used starting point for spotting whether someone is underweight, in a healthy range, overweight, or in the obese category.

How it works

BMI is weight in kilograms divided by height in meters squared. The World Health Organization categorizes the result: under 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30 or above is obese. The imperial formula multiplies pounds ÷ inches² by 703 to arrive at the same figure.

A quick example

Someone 5'9" and 170 pounds has a BMI of about 25.1 — just inside the overweight band, though a well-muscled athlete with the same numbers could still be lean. That caveat matters: BMI treats a linebacker and a couch potato identically if they weigh the same.

Tips for accurate results

Weigh yourself at the same time of day and in similar clothing to keep readings comparable. Pair BMI with a waist measurement or body-fat estimate for a fuller picture, especially if you carry a lot of muscle. And treat category boundaries as guides, not verdicts.

Enter your details to see your current BMI and category.

How to use this calculator

Four short steps, from gathering your numbers to double-checking the result.

Choose the unit system you can measure in accurately. Switching later converts nothing automatically, so set it once before typing and leave it alone.

Mathematical assumptions and review

  • Metric BMI = weight in kilograms / height in meters squared. Imperial BMI = weight in pounds / height in inches squared × 703; the displayed result is rounded to one decimal.
  • Adult category boundaries use the unrounded result: below 18.5, 18.5 to below 25, 25 to below 30, and 30 or above. BMI is a screening estimate, not a diagnosis; it does not distinguish fat from muscle and is not a child or pregnancy assessment.

Maintained by Add-ItUp. Formula outputs and the assumptions listed here were checked on . This is an internal check, not an independent audit or professional certification.

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