BMI Calculator

About the Bmi

This BMI calculator instantly works out your Body Mass Index using either metric (kilograms and centimetres) or imperial (pounds and feet/inches) units, and tells you which category your result falls into — underweight, normal weight, overweight, or obese. BMI, or Body Mass Index, is the simplest widely used tool for screening whether a person's weight is in a healthy range for their height. BMI is calculated by dividing your weight in kilograms by the square of your height in metres. For the metric version, that is BMI = weight(kg) ÷ height(m)². For imperial users, the calculator handles the feet-and-inches to metres conversion for you and applies the 703 multiplier so you never have to worry about the maths. For most adults, a BMI of 18.5–24.9 is considered normal or healthy, under 18.5 is underweight, 25–29.9 overweight, and 30 or above obese. BMI is a useful and convenient screening tool, but it is not a perfect measure of body fat. It does not distinguish between muscle and fat, so a muscular athlete may show a BMI in the overweight or even obese range despite having very low body fat — muscle is denser than fat, so heavier at the same height. Similarly, because it is based on overall weight, BMI can underestimate body fat in older adults who lose muscle and bone with age. It also does not account for where the fat is carried, which matters: abdominal fat (apple-shaped) is a higher health risk than fat carried around the hips and thighs. For this reason BMI is best used as one data point among several, alongside waist circumference, body fat percentage, and blood pressure. Use this calculator to know your own number and category, then speak to a health professional about what it means for you personally. The calculator works for anyone who wants a quick, standardised picture of their weight relative to height.