Quick answer: BMI = weight in kg ÷ (height in metres)². Below 18.5 is underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30+ obese. Enter your height and weight below for your exact BMI and health category.
📝 Worked example
70 kg, 1.75 m tall → BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 — healthy range (18.5–24.9).
✓ 100% FREE — No Signup Needed
Enter your height and weight for an instant body mass index, category, and healthy weight range.
For adults, a BMI below 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30 or above is obese. It is a useful starting point, not a diagnosis.
BMI compares weight with height. It does not directly measure body fat, muscle, bone density, or overall health.
BMI stands for body mass index. It is a screening measure that compares an adult's weight with the square of their height.
For most adults, the standard healthy range is 18.5 to 24.9. Individual health varies, so interpret the result alongside other health information.
BMI may overestimate body fat in muscular athletes. Children and teens require age- and sex-specific BMI percentiles, so this adult calculator is not suitable for them.
The calculator shows the weight range corresponding to a BMI of 18.5–24.9 for your height. “Ideal” weight is personal and may differ based on health, body composition, and medical advice.
Once a month is plenty for most people. Weight changes slowly, and checking too often can be discouraging because of normal daily fluctuations from water and food.
BMI can mislead for very muscular people, because muscle weighs more than fat. It also works less well for children, pregnant women, and older adults. Treat it as a starting point, not a final verdict.
For adults 18 and over. This calculator provides general information and is not medical advice.
Body Mass Index (BMI) is a simple number calculated from your height and weight that gives a quick picture of whether your weight sits in a healthy range. It was developed in the 1830s by the Belgian mathematician Adolphe Quetelet and is still used worldwide by doctors, fitness professionals, and health organisations as a first screening step.
BMI does not measure body fat directly. Instead, it estimates whether your weight is proportionate to your height, which is why it needs only two numbers and takes less than a minute. Millions of people check their BMI every month before starting a diet, joining a gym, or visiting a doctor, because it turns two measurements into one easy-to-understand result with a clear category: underweight, healthy, overweight, or obese.