This free BMI Calculator estimates body mass index (BMI) from your height and weight. It supports metric measurements (centimetres and kilograms) and imperial measurements (feet, inches and pounds). The result is intended as a general screening estimate for adults, not a diagnosis or a complete assessment of health.
How to use the BMI Calculator
- Choose Metric or Imperial units.
- Enter your height and weight in the selected units.
- Select Calculate BMI to see your estimate and its adult screening range.
- Use Reset to clear the form and start again.
BMI formula
For metric measurements, BMI is calculated by dividing weight in kilograms by height in metres squared:
BMI = weight (kg) ÷ [height (m) × height (m)]
For example, a person who weighs 70 kg and is 175 cm tall has a BMI of 70 ÷ (1.75 × 1.75), or approximately 22.9.
For imperial measurements, the equivalent calculation converts pounds and inches into the same metric relationship before calculating the result.
Understanding adult BMI ranges
- Below 18.5: Underweight range
- 18.5 to below 25: Healthy weight range
- 25 to below 30: Overweight range
- 30 or above: Obesity range
These commonly used adult categories are broad screening bands. They do not account for every difference in age, body composition or population background.
What BMI does not measure
BMI uses height and weight; it does not directly measure body fat, muscle mass, waist size or fat distribution. A muscular person may have a higher BMI without having excess body fat. Interpretation also differs for children and teenagers, during pregnancy, and in some older-adult and population contexts. This calculator is not designed to assess children.
Frequently asked questions
Is BMI a diagnosis?
No. BMI is a screening measure. A healthcare professional may consider it alongside other measurements, medical history and individual circumstances.
Can I use pounds and feet?
Yes. Select Imperial and enter feet, additional inches and weight in pounds.
Why might BMI not reflect my fitness?
BMI does not distinguish muscle from fat or show where body fat is carried, so it cannot describe fitness or health on its own.
Important: Use this result for general information only. If you have health concerns or need an individual assessment, speak with a qualified healthcare professional.