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Calculate BMI
Calculate your Body Mass Index and find out if you're in a healthy weight range.
Enter your height and weight and hit
Calculate BMI
Our free BMI calculator lets you calculate your Body Mass Index in seconds using either metric (kg and cm) or imperial (lbs and inches) measurements. BMI is a widely used screening tool to categorise weight status — underweight, healthy weight, overweight or obese. The calculator shows your BMI score, your category, a visual gauge, and the healthy weight range for your height.
BMI is calculated by dividing your weight in kilograms by the square of your height in metres: BMI = weight (kg) ÷ height (m)². For imperial measurements, the formula is: BMI = (weight in lbs × 703) ÷ height in inches². The World Health Organisation defines a healthy BMI range as 18.5 to 24.9.
According to the World Health Organisation (WHO), a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.
BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, bone density, age or sex distribution of fat. Athletes may have a high BMI due to muscle. It's best used alongside other health measurements.
A BMI of 30 or above is classified as obese (Class I). A BMI of 35–39.9 is Class II obese, and 40 or above is Class III (severe) obesity. These classifications are the same for both men and women.
Divide your weight in kilograms by your height in metres squared. For example, 70kg ÷ (1.75m × 1.75m) = 70 ÷ 3.0625 = 22.9 BMI, which is in the healthy range.
The healthy BMI range is the same for men and women: 18.5 to 24.9. However, women naturally carry a higher percentage of body fat at the same BMI, so some health professionals use adjusted ranges for older women.
The standard BMI ranges apply to adults aged 18 and over. For children and teenagers, BMI is calculated the same way but interpreted differently using age and sex-specific percentile charts.