BMI calculator
Calculate your body mass index from height and weight, see the standard adult category, and the healthy-weight range for your height. Metric or US units.
What BMI is good for
BMI is a simple ratio of weight to height squared. At the population level it tracks body fat reasonably well, which is why doctors use it as a first screen. For an individual it is a starting point: it says nothing about muscle, fat distribution or fitness.
US: BMI = 703 × weight(lb) ÷ height(in)²
| BMI | Adult category (WHO) |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25–29.9 | Overweight |
| 30 and above | Obesity |
For a fuller picture, add a body fat estimate and a waist measurement.
Questions
What is a healthy BMI?
For adults, the World Health Organization classifies a BMI of 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight and 30 or above as obesity. Some health bodies use lower cut-offs for people of Asian descent.
Is BMI accurate?
BMI is a quick screening number, not a diagnosis. It does not separate muscle from fat or show where fat is stored, so a muscular person can have a high BMI and be lean. Waist measurement adds useful information.
How is BMI calculated?
Weight in kilograms divided by height in meters squared. In US units: weight in pounds × 703, divided by height in inches squared.
Does BMI work for children?
Not with these categories. Children and teens use age- and sex-specific BMI percentiles.
Sources
- World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894; 2000.
- U.S. Centers for Disease Control and Prevention. Adult BMI categories.
Built and checked by Ingrid Solberg. Last reviewed October 22, 2026. All formulas: formulas & sources.