Calculate adult body mass index (BMI) using metric units (kilograms and centimetres) or imperial units (pounds, feet and inches). Enter your height and weight below to see your BMI and adult weight-status category.
Adult BMI categories
For adults aged 20 and older, the CDC uses the following categories. Boundary values do not overlap: for example, a BMI of exactly 25 is in the overweight category.
| BMI | Adult category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to below 25 | Healthy weight |
| 25 to below 30 | Overweight |
| 30 or higher | Obesity |
Obesity is also divided into Class 1 (30 to below 35), Class 2 (35 to below 40), and Class 3 (40 or higher). See the CDC adult BMI categories.
How BMI is calculated
Metric BMI is weight in kilograms divided by height in metres squared: BMI = kg ÷ m². With imperial measurements, use BMI = 703 × lb ÷ in². For example, 70 kg at 1.80 m gives a BMI of 21.6. See the complete BMI formula and worked examples, or use the metric BMI chart and imperial BMI chart.
What the result can and cannot tell you
BMI is a screening measure, not a diagnosis. It does not distinguish body fat from muscle or bone and does not show where body fat is distributed. A healthcare professional may consider BMI together with medical history, physical examination and other health measures.
Adult categories should not be used to interpret a child or teenager’s result. For ages 5–19, use the sex- and age-specific girls BMI calculator or boys BMI calculator.
Information reviewed 29 August 2026. This calculator provides general information and is not a substitute for medical advice.