Free online BMI Calculator
Three simple steps
- Choose metric or imperial units, then enter your weight and height.
- Read your BMI and its position on the adult reference scale.
- Use the category and reference-weight interval as context, rather than a health diagnosis.
Understand your result
Body mass index (BMI) compares weight with height. It is a screening measure that can help start a health discussion; it does not measure body fat directly or diagnose a person’s health.
Worked example
For 70 kg and 175 cm, convert height to 1.75 metres. BMI = 70 ÷ (1.75 × 1.75) = 22.9. The calculator also gives an approximate weight interval based on the same adult reference thresholds.
Read the adult BMI scale
| BMI | Reference category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to below 25 | Healthy-weight reference |
| 25 to below 30 | Overweight |
| 30 or above | Obesity category |
Category boundaries apply to the unrounded BMI. Displayed rounded values near a boundary can look similar while belonging to different categories.
Who should use another assessment?
These categories are commonly used for adults aged 20 and older. Children and teens need age- and sex-specific assessment. Pregnancy, high muscle mass, and individual health circumstances also limit what this number can tell you. A reference-weight interval is not a personal target or instruction to gain or lose weight.
Formula reference
CDC: Adult BMI categories and interpretation. Discuss concerns with a qualified healthcare professional.