myBMI Calculator
Calculate your Body Mass Index. Supports both metric (kg/cm) and imperial (lb/in) units.
About the BMI Calculator
Body Mass Index (BMI) is a simple numerical measure calculated from a person's height and weight. It was developed in the 19th century by Belgian statistician Adolphe Quetelet and has been used by the World Health Organization as a population-level health screening tool since the 1980s.
BMI categories (WHO standard)
- Below 18.5 — Underweight
- 18.5 – 24.9 — Normal (healthy) weight
- 25.0 – 29.9 — Overweight
- 30.0 – 34.9 — Obese Class I
- 35.0 and above — Obese Class II+
Limitations of BMI
BMI does not distinguish between muscle and fat mass. Athletes and heavily muscled individuals may have a high BMI despite low body fat. Elderly people may have a normal BMI but carry excess fat due to muscle loss. For a complete health picture, BMI should be used alongside other measurements such as waist circumference.
Metric vs imperial
Our calculator supports both metric units (kilograms and centimetres) and imperial units (pounds and inches). Switch between them using the toggle at the top of the calculator — all values convert automatically.
BMI and ethnicity
Research shows that people of South Asian, Chinese, Japanese, and other East Asian descent have a higher risk of metabolic complications at lower BMI thresholds than people of European descent. The WHO recommends lower cut-off points for Asian populations: overweight from 23 rather than 25, and obese from 27.5 rather than 30. This calculator uses standard WHO thresholds; consult your GP for personalised assessment.
- South Asian populations — overweight from BMI 23, obese from 27.5
- Black populations — some evidence suggests higher muscle mass may mean standard thresholds overestimate risk
- Older adults — a BMI of 25-27 may be protective in people over 65
- Children — BMI is assessed using age- and sex-specific growth charts, not adult thresholds