BMI Calculator
Body Mass Index, classified with the WHO standard.
Use this free BMI calculator to find your body mass index from your height and weight. This body mass index calculator supports both metric and imperial units and classifies your result using the official WHO standard.
Enter your measurements above.
This calculator provides estimates based on published formulas and methodologies. Results are for educational and informational purposes only and should not be considered medical advice.
Understanding your result
BMI is a screening measure that estimates body fat from height and weight. It is widely used because it requires only two simple measurements.
The World Health Organization classifies adults into Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above), with obesity further split into Class I, II and III.
BMI does not distinguish muscle from fat or account for sex, age, or body composition. Athletes with high muscle mass may read as overweight, while older adults may carry more fat at a normal BMI.
Methodology
BMI is calculated by dividing body weight in kilograms by the square of height in metres (kg/m²). Imperial inputs are converted to metric before calculation.
Category thresholds follow the WHO international classification of adult underweight, overweight and obesity.
The healthy weight range shown for your height is the band of weights that produce a BMI between 18.5 and 24.9.
The formula
BMI equals mass in kilograms divided by height in metres squared.
- For imperial units: BMI = 703 × weight (lb) ÷ height (in)²
- Healthy weight range = 18.5 × height(m)² to 24.9 × height(m)²
References
Frequently asked questions
Is BMI accurate for everyone?
BMI is a population-level screening tool, not a diagnosis. It does not measure body fat directly and can misclassify muscular individuals, older adults, and some ethnic groups. Use it as one data point alongside other measures.
What is a healthy BMI?
The WHO defines a healthy BMI for adults as 18.5 to 24.9. Below 18.5 is classified as underweight and 25 or above as overweight.
Does BMI differ for men and women?
The standard adult BMI formula and thresholds are the same for men and women. However, at the same BMI, women tend to have more body fat than men, which is a known limitation.
How is BMI calculated from height and weight?
BMI divides your weight in kilograms by your height in metres squared. For pounds and inches, multiply weight by 703 and divide by height in inches squared.
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