BMI is a screening index based on weight and height to classify underweight, healthy weight, overweight, and obesity.

Is BMI accurate for everyone?

BMI is a screening tool and does not measure body fat directly. Accuracy varies with muscle mass, age, sex, and ethnicity.

BMI Calculator

Underweight <18.5; Healthy 18.5–24.9; Overweight 25.0–29.9; Obesity ≥30.0.

Calculate your Body Mass Index (BMI) using metric or imperial units. Get instant interpretation using WHO adult categories and see the formula used.

Metric (kg, cm) Imperial (lb, ft+in)

Weight (kg) *

Height (cm) *

BMI —

Category (WHO) —

Enter your measurements to see your BMI and category.

Formula

Metric: \\( BMI = \\dfrac{\\text{kg}}{(\\text{m})^2} \\)

Imperial: \\( BMI = 703 \\times \\dfrac{\\text{lb}}{(\\text{in})^2} \\)

What is BMI and how is it used?

BMI is a screening index that relates weight to height. It does not directly measure body fat but is widely used for population-level assessment.

What are the standard adult BMI categories?

Underweight: < 18.5 · Healthy: 18.5–24.9 · Overweight: 25.0–29.9 · Obesity: ≥ 30.0.

Does BMI apply to athletes or children?

For muscular individuals BMI can overestimate body fat. For children/teens use age- and sex-specific BMI percentiles, not this adult tool.

Tool developed by Ugo Candido. Content verified by CalcDomain Editorial. Last reviewed: September 13, 2025.