Body mass index · metric or US units
BMI Calculator
Last updated: October 2026
Written by Jessica Hill
Calculate your body mass index from your height and weight in pounds and inches or kilograms and centimeters. The result is rounded to one decimal place and shown with its WHO weight band.
- Pounds or kilograms
- WHO weight bands
- Runs on your device
Body mass index, or BMI, compares weight to height. It is a quick screening number used by doctors and public health bodies, but it does not measure body fat directly. Read the notes below to understand what your number does and does not tell you.
How To Use The BMI Calculator
- Choose your units: pounds and inches, or kilograms and centimeters.
- Enter your weight and height. In US units, give height in feet plus inches, for example 5 ft 7 in.
- Read your BMI and the WHO band it falls into.
BMI Formula
BMI Categories For Adults
| BMI | WHO category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25 to 29.9 | Overweight |
| 30 or above | Obesity |
Worked Examples
US Units
- Input
- 150 lb and 5 ft 7 in, which is 67 inches.
- Steps
- 703 × 150 ÷ 67² = 105,450 ÷ 4,489
- Result
- 23.5, in the 18.5–24.9 band.
Metric Units
- Input
- 70 kg and 170 cm, which is 1.70 m.
- Steps
- 70 ÷ 1.70² = 70 ÷ 2.89
- Result
- 24.2, in the 18.5–24.9 band.
This calculator is for general information and learning. It is not a diagnosis. If you have questions about your weight or health, talk to a doctor or another qualified health professional.
Check another height or weight
Switch units at any time. Nothing you enter is stored.
Frequently Asked Questions
Is BMI accurate?
BMI is a useful population-level screening tool, but it is only an estimate for one person. Waist size, body composition and other health measures give a fuller picture.
Can I use this for children?
No. For people under 20, BMI is compared with growth charts for the same age and sex. Ask a pediatrician or use a dedicated child BMI chart.
How do I convert my height to inches?
Multiply the feet by 12 and add the inches. 5 ft 7 in is 5 × 12 + 7 = 67 inches. The calculator does this for you.
Is my health information saved?
No. The calculation happens in your browser. Your height and weight are not sent to a server or stored.