BMI Calculator
Body Mass Index (BMI) is a screening tool that estimates whether your weight is in a healthy range relative to your height. It's widely used by doctors and health organisations as a quick first assessment.
| BMI Range | Category | Health Risk |
|---|---|---|
| < 18.5 | Underweight | Nutritional deficiency, osteoporosis |
| 18.5–24.9 | Normal weight | Lowest risk |
| 25.0–29.9 | Overweight | Slightly elevated |
| 30.0–34.9 | Obese — Class I | Moderate |
| 35.0–39.9 | Obese — Class II | High |
| ≥ 40.0 | Obese — Class III | Very high |
Source: World Health Organisation. This classification applies to adults aged 18 and over. Children and teenagers use age- and sex-adjusted percentile charts.
BMI divides your weight in kilograms by the square of your height in metres. The metric toggle converts imperial inputs automatically before calculating.
Below 18.5 is considered underweight. 18.5–24.9 is the healthy range. 25–29.9 is overweight. 30 and above is classified as obese (split into three classes). The colour bar highlights which category you fall into.
BMI doesn't distinguish between muscle and fat mass — athletes may show a high BMI despite very low body fat. It also doesn't account for age, sex, or where fat is distributed. Use it alongside other health metrics like waist circumference and body fat percentage.
- •For the most accurate result, measure height without shoes and weight first thing in the morning.
- •Children and teenagers use a different age/sex-adjusted BMI scale — this calculator is for adults (18+).
- •Check the Body Fat and Ideal Weight calculators for a more complete picture of your body composition.