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Health & Fitness

BMI Calculator

Work out your body mass index from your weight and height, see which WHO category it falls in, and the weight range that counts as healthy for your height.

By Aditya Kr Sharma Formula checked

  • Free
  • Instant
  • No sign-up

How to use this calculator

  1. Pick what to find Choose a mode, or start with the first box.
  2. Enter your numbers Type your values into the boxes.
  3. Read the result See the answer and the working, then copy or share it.
Units

Enter your weight and height, then press Calculate BMI.

How to use the BMI calculator

  1. Choose metric or US units.
  2. Enter your weight and height.
  3. Press Calculate BMI to see your BMI, its WHO category and your healthy weight range.

BMI categories for adults

BMIWHO category
Under 18.5Underweight
18.5 – 24.9Healthy weight
25 – 29.9Overweight
30 – 34.9Obesity class I
35 – 39.9Obesity class II
40 and overObesity class III

What BMI Prime means

BMI Prime is your BMI divided by 25, the top of the healthy range. Under 1.0 is within or below the healthy range; 1.2 means 20% above its upper limit.

Frequently asked questions

How is BMI calculated?

BMI = weight in kilograms ÷ height in metres squared. In pounds and inches: BMI = 703 × lb ÷ in². The calculator converts US units to metric first and shows the working.

What is a healthy BMI?

For adults the WHO calls 18.5 to 24.9 a healthy weight, 25 to 29.9 overweight and 30 or more obesity. Under 18.5 is underweight.

What is my healthy weight?

The weights that give a BMI of 18.5 to 24.9 at your height. At 1.75 m that is about 56.7 to 76.3 kg; the result shows the range for the height you enter.

Is BMI accurate?

It is a quick screen, not a measurement of fat. Athletes with a lot of muscle can have a high BMI and low body fat, and older adults can have a normal BMI with little muscle. Waist size and a body fat estimate add useful detail.

About these results

BMI is a screening number for adults. It does not measure body fat directly and reads high for muscular people; it is not a diagnosis.

Children and teenagers need age- and sex-specific BMI percentiles, which this calculator does not use.

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