BMI Calculator – Body Mass Index Calculator
Find your Body Mass Index in seconds, see exactly where you sit on the WHO scale, and learn the healthy weight range for your height.
Understanding BMI
Body Mass Index (BMI) is calculated as weight (kg) divided by height (m) squared. It is a simple, inexpensive screening tool used by clinicians and public health officials worldwide.
| Category | BMI range | Health risk |
|---|---|---|
| Underweight | < 18.5 | Increased risk of nutrient deficiency |
| Normal weight | 18.5 – 24.9 | Lowest risk |
| Overweight | 25 – 29.9 | Increased |
| Obese (Class I) | 30 – 34.9 | Moderate |
| Obese (Class II) | 35 – 39.9 | Severe |
| Obese (Class III) | ≥ 40 | Very severe |
BMI limits
Because BMI does not measure body composition, it can mislabel muscular individuals as overweight and miss "skinny-fat" individuals (those with normal weight but high body fat). Pair BMI with waist circumference, body-fat percentage, and overall fitness for a complete view.
Common questions
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered "normal" weight by the World Health Organization. However BMI is a screening tool, not a diagnosis — read on for limits.
Is BMI accurate for athletes?
BMI does not differentiate between fat and muscle, so very muscular individuals can register as overweight or obese while being lean and healthy. Athletes should use our Body Fat Calculator for a better picture.
Does BMI work for children?
The same formula is used, but the categorisation is based on age- and sex-specific percentile charts (CDC growth charts). This calculator is intended for adults aged 18+.
Which is better — BMI or body fat percentage?
Body-fat percentage is a more accurate marker of health, but it is harder to measure. BMI is a quick, free, large-scale screening tool. Use BMI for a baseline and body-fat % for nuance.