BMI calculator
Body mass index for adults, with the WHO category for your result.
BMI
Rounded for displayBMI: ≈ 22.9
- WHO category
- Normal weight
- BMI 18.5 at your height
- ≈ 56.7 kg
- BMI 24.9 at your height
- ≈ 76.3 kg
- Underweight: 10 – 18.5
- Normal weight: 18.5 – 25
- Pre-obesity: 25 – 30
- Obesity I: 30 – 35
- Obesity II: 35 – 40
- Obesity III: 40 – 45
How it works
Body mass index is weight in kilograms divided by height in metres squared. Imperial values are converted exactly (1 lb = 0.45359237 kg, 1 in = 2.54 cm), which is equivalent to about 703 × lb ÷ in².
The categories are the World Health Organization adult bands: below 18.5 underweight, 18.5–24.9 normal, 25.0–29.9 pre-obesity, 30.0–34.9 obesity class I, 35.0–39.9 class II, 40 and over class III.
BMI is a screening measure. It does not tell muscle from fat and is not used on its own for diagnosis. For children and teenagers, BMI-for-age percentiles are used instead; this calculator does not compute them.
This is a general estimate, not medical advice. For personal guidance, speak to a doctor or registered dietitian.
Formula
BMI = weight (kg) ÷ height (m)² BMI ≈ 703.07 × weight (lb) ÷ height (in)²
Worked example
A weight of 70 kg at a height of 1.75 m gives 70 ÷ 1.75² = 22.9, in the normal range. At that height, a BMI of 18.5 to 24.9 corresponds to 56.7 to 76.3 kg.
Questions people ask
What is a healthy BMI?
For adults, the WHO classes 18.5 to 24.9 as normal weight. Some health bodies use lower cut-offs for people of Asian descent.
Is BMI accurate for athletes?
Not always. Muscle is dense, so very muscular people can have a high BMI without excess fat. Waist measurement or body-fat estimates add context.
Can I use this for a child?
No. Children and teenagers are assessed with BMI-for-age percentile charts, which take age and sex into account.