BMI — Body Mass Index Calculator — Free Online Calculator

Input Parameters

Age (2 - 120)

Gender

Unit System

Height (cm)

Weight (kg)

Calculated BMI

22.9 kg/m²

Adult BMI Categories (WHO Classification)

For adults aged 20 and older, standard BMI categories are defined by the World Health Organization (WHO) as follows:

Category	BMI Range (kg/m²)	BMI Prime Range
Severe Thinness	< 16.0	< 0.64
Moderate Thinness	16.0 – 16.9	0.64 – 0.68
Mild Thinness	17.0 – 18.4	0.68 – 0.74
Normal / Healthy Weight	18.5 – 24.9	0.74 – 1.00
Overweight	25.0 – 29.9	1.00 – 1.20
Obese Class I (Moderate)	30.0 – 34.9	1.20 – 1.40
Obese Class II (Severe)	35.0 – 39.9	1.40 – 1.60
Obese Class III (Very Severe)	≥ 40.0	≥ 1.60

Children & Teens BMI-for-Age Categories (CDC Classification)

For children and adolescents aged 2 to 19, BMI is assessed relative to other children of the same age and biological sex using CDC percentile curves:

Category	Percentile Range	Interpretation
Underweight	< 5th percentile	Weight is lower than 95% of peers of the same age/sex.
Normal / Healthy Weight	5th percentile to < 85th percentile	Optimal weight range for healthy growth and development.
Overweight	85th percentile to < 95th percentile	Weight is higher than 85% of peers of the same age/sex.
Obese	≥ 95th percentile	Weight is higher than 95% of peers of the same age/sex.

Calculate your Body Mass Index (BMI) and find your weight category instantly. Supports adult classification and CDC child/teen percentile calculations.

How it Works & Formula

BMI = weight(kg) / height(m)²

For adult systems, categories are constant. For children and teens aged 2 to 19, the CDC BMI-for-age percentiles compare values against growth standards.

Practical Examples

Example 1: Standard Adult Sizing

An adult weighing 70 kg and standing 1.75 meters tall has a BMI of 22.86, placing them in the normal weight range.

Frequently Asked Questions

What is BMI?

BMI (Body Mass Index) is a measurement of a person's weight relative to their height. It is widely used as a screening tool to classify individuals into underweight, healthy weight, overweight, or obese categories.

How is children's BMI calculated differently?

While the formulas for children and adults are the same, their thresholds differ. Children and teens are rapidly growing, so their BMI values are evaluated relative to peers of the same age and gender using CDC percentile charts.

What is BMI Prime?

BMI Prime is a ratio of your actual BMI to the upper limit of the healthy BMI range (25.0). A BMI Prime value between 0.74 and 1.00 is considered healthy.

What is the Ponderal Index?

The Ponderal Index is similar to BMI but scales weight relative to height cubed (weight/height³). It is considered a more fair metric for extremely tall or short individuals.

BMI — Body Mass Index Calculator