Calculate your Body Mass Index — metric or imperial
BMI (Body Mass Index) is a number calculated from your weight and height. It's used by doctors and health organizations worldwide as a quick screening tool to categorize whether a person has a healthy weight. The formula is straightforward: BMI = weight(kg) ÷ height(m)².
For example: a person who weighs 70kg and is 175cm tall has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9, which falls in the normal range.
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Increased risk (nutritional deficiency, bone loss) |
| 18.5 – 24.9 | Normal weight | Lowest risk |
| 25.0 – 29.9 | Overweight | Increased risk |
| 30.0 – 34.9 | Obese Class I | High risk |
| 35.0 – 39.9 | Obese Class II | Very high risk |
| 40.0 and above | Obese Class III | Extremely high risk |
BMI is a useful but imperfect tool. It doesn't distinguish between muscle and fat — a muscular athlete may have a high BMI despite having low body fat. It also doesn't account for age, sex, ethnicity, or where fat is distributed on the body. BMI is best used as one data point among several, in combination with waist circumference, blood pressure, and other health markers.
For health decisions, always consult a qualified medical professional. BMI is a screening tool, not a diagnostic one.
For weight unit conversions, use our weight converter. For financial health, check our EMI calculator and personal budget guide.
BMI 25.0–29.9 is overweight. BMI 30+ is obese. Below 18.5 is underweight. Normal healthy range is 18.5–24.9 according to WHO guidelines.
BMI doesn't distinguish muscle from fat. A muscular athlete may have high BMI despite low body fat. BMI is a screening tool — not a diagnostic measure. Use alongside waist circumference and other health markers.
BMI = 703 × weight(lbs) ÷ height(inches)². Example: 150 lbs, 5'8" (68 inches): BMI = 703×150÷68² = 703×150÷4,624 = 22.8.