How Do You Calculate the BMI Index?


Quick Answer

To calculate the Body Mass Index, or BMI, convert the weight and height to kilograms and meters, find the square of the height, and divide the weight by the square of the height. Refer to the BMI chart to determine the weight status of underweight, normal, overweight and obese.

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Full Answer

  1. Convert the weight to kilograms

    To convert the weight from pounds to kilograms, multiply the weight by 0.45. For example, a person who weighs 125 pounds weighs 56.25 kilograms.

  2. Convert the height to meters

    To convert the height from inches to centimeters, multiply the height by 0.025. For example, a person who is 5 feet, 3 inches tall, is 63 inches or 1.575 meters.

  3. Find the square of the height

    Multiply the height in meters by itself. For example, 1.575 multiplied by 1.575 is 2.48.

  4. Calculate the BMI

    Divide the weight by the square of the height. In the example, 56.25 divided by 2.48 is 22.7. So a person who is 63 inches tall and weighs 125 pounds, has a BMI of 22.7.

  5. Estimate the weight status

    Check the standard BMI chart for an interpretation of the number. If the BMI is under 18.5, the person is underweight. If the BMI is between 18.5 to 24.9, the person is normal. If the BMI is between 25 to 29.99, the person is overweight. If the BMI is over 30, the person is obese.

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