BMI Calculator

Check your body mass index

Body Mass Index (BMI) is a quick screening number that relates your weight to your height. Enter your measurements in either metric or imperial units and this calculator returns your BMI along with the weight category it falls into. It runs entirely in your browser, so your measurements are never uploaded.

The BMI formula

For example, someone 1.75 m tall weighing 70 kg has a BMI of 70 ÷ (1.75 × 1.75) ≈ 22.9 — within the healthy range.

Adult BMI categories

• Under 18.5 — underweight
• 18.5 – 24.9 — healthy weight
• 25 – 29.9 — overweight
• 30 and above — obese

BMI is a general screening tool, not a medical diagnosis. It doesn't distinguish muscle from fat and isn't intended for children, athletes or during pregnancy. Speak with a healthcare professional for advice about your individual health.

A worked example

Take someone 1.75 m tall weighing 82 kg. Squaring the height gives 1.75 × 1.75 = 3.0625, and 82 ÷ 3.0625 = a BMI of 26.8 — just into the "overweight" band. To reach the top of the healthy range (BMI 24.9) they'd weigh about 76 kg. Switch the calculator to imperial and the same person is 5 ft 9 in, 181 lb, and the formula 703 × 181 ÷ 69² returns the same 26.8. The tool converts for you — you only pick the units you have to hand.

What BMI doesn't tell you

BMI is a fast, useful screen, but it only knows your height and weight — not what that weight is made of. Because muscle is denser than fat, a lean, muscular athlete can read "overweight" while carrying very little fat, and an older person who has lost muscle can read "healthy" while carrying too much. It also says nothing about where fat sits, and abdominal fat carries more health risk than fat elsewhere.

That's why BMI is best read alongside other measures. Estimate your composition with the body fat calculator, find a sensible target with the ideal weight calculator, and plan intake with the TDEE calculator. For more on what the numbers mean, read what is a healthy BMI.

Frequently asked questions