BMI Calculator

Body Mass Index (BMI) is the simplest population-level screen for whether your weight is in a healthy range for your height. It is calculated by dividing your weight in kilograms by the square of your height in metres. A 70 kg adult who stands 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9.

The World Health Organization brackets adult BMI as under 18.5 (underweight), 18.5 to 24.9 (healthy weight), 25 to 29.9 (overweight) and 30 or above (obese). These cut-offs are the same for adult men and women, because the formula deliberately ignores body composition — it maps a single number onto a single height. That is also its biggest weakness: a muscular athlete and a sedentary person of the same height can share a BMI while carrying very different amounts of fat.

BMI also does not account for age, bone density, ethnicity or where fat is stored. Abdominal fat is more metabolically harmful than fat on the hips, yet BMI cannot tell them apart. Because of this, a rising BMI is best read as a prompt to look at other measures — waist circumference, body-fat percentage, waist-to-height ratio and how your clothes fit — rather than as a diagnosis on its own.

This calculator adds two useful numbers. The healthy weight range shows the lightest and heaviest weight that keeps you inside the 18.5–24.9 band for your exact height, so you can see how far you sit from it. BMI prime is simply your BMI divided by 25; a value below 1.0 means you are under the overweight threshold, and it is a quick way to compare two people of different heights on the same scale.

BMI was designed for tracking large groups over time, not for judging an individual. Treat it as one signal among several, and speak to a healthcare professional if you are concerned about your weight rather than making decisions from this number alone.

This calculator returns estimates for general information only. It is not medical advice, diagnosis or treatment, and it cannot replace an assessment by a qualified health professional. Individual results vary, and figures such as calorie needs, body-fat percentage and heart-rate zones are approximations based on population averages rather than measurements of you.