BMI Calculator - Body Mass Index

Created by Luis Hoyos
Based on research by
Nuttall FQ. Body Mass Index: Obesity, BMI, and Health: A Critical Review. Nutrition Today (May 2015)See 1 more source
Aune D, Sen A, Prasad M, Norat T, Janszky I, Tonstad S, Romundstad P, Vatten LJ. BMI and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants. BMJ (May 2016)
Last updated: Jul 09, 2022

If you're searching for how to calculate BMI (Body mass index), this BMI calculator is what you need. Enter the height and weight, and the BMI calc will provide the result immediately, conveniently allowing you to enter height and weight in units of your choice.

Apart from finding what is your BMI, you'll figure out if you are underweight, at a normal weight, or overweight (and need to burn some calories cut your gas cost at the same time).

🙋 Knowing how to calculate your BMI can give you insight into your level of health, but there's another mass-height measure that could give you an even better insight, called body surface area (BSA). Your BSA is a predictor of coronary artery calcium, a severe medical concern that BMI cannot predict. BSA is also a better indicator of metabolic rate than body weight. Learn more about it in our BSA calculator.

What is BMI?

The BMI is a quantity that doctors and nutritionists use to determine if a person is overweight or under-weight and to what extent. We calculate it by dividing the person's mass (in kilograms) by the square of their height (in meters).

Obesity and BMI
Obesity and BMI. Via Wikimedia Commons

How do I calculate BMI? BMI formula

  • To calculate your BMI with your mass in kilograms and height in meters, use the following formula:

    BMI = Masskg/Heightm2

    where:

    • BMI — Body mass index;
    • Masskg — your mass in kilograms (kg); and
    • Heightm — your height in meters (m);
  • If you only know the mass in pounds and the height in inches, multiply the formula by 703:

    BMI = 703 × Masslb/Heightin2

    where:

    • Masslb — your mass in pounds (lb); and
    • Heightin — your height in inches (in);

Our weight converter can be helpful if you need to convert between kg and lb. For height, you can do the same using our length converter.

What is BMI Prime?

The BMI Prime is a nifty modification to our own BMI calculator. It's a decimal number where 1.0 is the upper limit to the "normal BMI" range. If your BMI Prime is more than 1, then you have some weight to lose.

As the BMI upper limit before reaching overweight is 25, we calculate BMI Prime by dividing the conventional BMI by 25:

BMI Prime = BMI/25

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