BMI Calculator
BMR Calculator
WHR Calculator
Use this metric and imperial BMI calculator tool to work out your body mass index and get an indication of whether your weight might be affecting your health. This BMI tool is intended for use by men and women of 18 years and over.
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Disclaimer: Whilst every effort has been made in building our calculator tools, we are not to be held liable for any damages or monetary losses arising out of or in connection with their use. The content here should be used only as a guide and should not replace medical advice. Please refer to a qualified health professional if you have any questions or concerns about your weight or body composition. For example, a person who is very muscular may have a higher BMI, while their body fat is actually perfectly healthy. Use it to find out about your BMI, but remember the limitations of this metric.
Full disclaimer.
BMI calculations
Body Mass Index is calculated using either the metric or imperial BMI formulas. In both cases, you divide your weight by your height raised to the power of 2. With the imperial BMI formula, you then multiply the resulting figure by 703.
If you wish to calculate your BMI manually rather than using the BMI calculator, I've included some simple instructions and formulas below. It's important that if you are doing these, you ensure that your units are in the same unit system (metric or imperial) and the correct corresponding unit.
If you need to convert between units of weight, use our kilos and pounds converter.
To calculate your BMI
1
Divide your weight (lb) by your height (in):Example: 1549 ÷ 71in = 2.160
2
Divide your answer from part 1 by your height again:Example: 2.160 ÷ 71 = 0.03098
3
Multiply your answer from part 2 by 703:Example: 0.03098 × 703 = 21.41
For kg and meters/metres
1
Divide your weight (kg) by your height (m):Example: 85kg ÷ 1.83m = 30.519
2
Divide your answer from part 1 by your height again:Example: 30.519 ÷ 1.83 = 19.41
Note that you can convert between units of height with our height converter or our cm to feet converter.
BMI formula for men and women
The official formula for BMI was devised in the 1830s by Belgian mathematician Adolphe Quetelet.
Learn more about how to use these formulas with our unit-by-unit walkthrough on the BMI formula. An interactive BMI chart is also available to use.
What is BMI?
The body mass index calculation is the calculation of your body weight in relation to your height and is commonly used as an indicator of whether you might be in a risk category for health problems caused by your weight. Using a BMI calculator such as the one on this page, you enter your weight and height measurements.
Below are the BMI classifications for men and women established by the World Health Organization (WHO) and endorsed by a number of major health organizations. References: The practical guide: identification, evaluation, and treatment of overweight and obesity in adults – National Institutes of Health (NIH), National Heart, Lung, and Blood Institute (NHLBI).
| Body Mass Index (kg/m2) | Classification |
|---|
| less than 18.5 | underweight |
| 18.5 – 24.9 | normal weight |
| 25 – 29.9 | overweight |
| 30 – 34.9 | class I obese |
| 35 – 39.9 | class II obese |
| 40 and above | class III obese |
It is important to remember that BMI measurements do not make a distinction between whether you are male or female, whether you have a large or small body frame, whether you have high muscle mass and the areas in which fat is distributed around your body. So, someone who has a very muscular physique (a body builder, for example) may have a high BMI without having excess fat. For this reason, BMI is not an indicator of obesity on its own.
Some alternative methods to BMI, including the waist-to-hip ratio, are discussed in our article, 5 alternatives to BMI. There's also a good section about BMI on the CDC website.
BMI and BMR
As well as BMI, this website also features a BMR calculator that allows you to calculate your basal metabolic rate (the number of calories you might burn in a day if you are inactive).