BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight, and see which general weight category it falls into.
BMI is a general screening measure and doesn't account for muscle mass, age, or body composition. It is not a diagnosis. See our Disclaimer.
The formula
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)².
Standard BMI categories
- Below 18.5 — Underweight
- 18.5–24.9 — Normal weight
- 25–29.9 — Overweight
- 30 and above — Obesity
Worked example
A person weighing 70 kg at 175 cm (1.75 m) tall has a BMI of 70 ÷ 1.75² ≈ 22.9, which falls in the normal weight range.
Method and sources
The categories are the World Health Organization's standard adult BMI classification (18.5, 25 and 30). The category is read straight from the number, with no adjustment for age, sex, ethnicity or body composition, and some guidelines use different cut-offs for specific populations — ask a healthcare professional how to interpret your result. The worked example was recalculated independently in September 2026.
Limitations of BMI
BMI doesn't distinguish between muscle and fat, so athletes with high muscle mass can show a misleadingly high BMI. It also doesn't account for age, sex, or where fat is distributed on the body. It's best used as a general screening starting point, not a full health assessment.
Frequently asked questions
Is BMI accurate for everyone?
No. It's a population-level screening tool that works reasonably well for most adults but can be misleading for athletes, older adults, pregnant women, and children, where other measures are more appropriate.
What should I do if my BMI is outside the normal range?
BMI alone isn't a diagnosis. If you have concerns about your weight or health, a doctor can assess your overall health using additional measures beyond BMI.