BMI Calculator

Calculate your Body Mass Index.

Enter your height and weight to instantly calculate your BMI. Supports both metric (kg/cm) and imperial (lbs/ft) units.

Weight (kg)

Height (cm)

Age (optional — for context)

Understanding Your BMI

Body Mass Index (BMI) is a simple numerical measure of a person's weight relative to their height. It was developed in the 1830s by Belgian mathematician Adolphe Quetelet and remains one of the most widely used health screening tools worldwide. While BMI provides a useful starting point for assessing weight-related health risks, it does not directly measure body fat or account for factors such as muscle mass, age, gender, and where fat is distributed in the body. A comprehensive health evaluation should include BMI alongside other measurements.

BMI Categories (WHO Standard)

BMI Range	Category	Health Risk
Below 18.5	Underweight	Nutritional deficiency risk
18.5 – 24.9	Normal Weight	Lowest health risk
25.0 – 29.9	Overweight	Moderate health risk
30.0 – 34.9	Obese Class I	High health risk
35.0 – 39.9	Obese Class II	Very high health risk
40.0+	Obese Class III	Extremely high health risk

Frequently Asked Questions

What is BMI?

BMI (Body Mass Index) is a measure of body fat based on height and weight. It is calculated by dividing weight in kilograms by height in meters squared (kg/m²). It is widely used as a screening tool to categorize people as underweight, normal weight, overweight, or obese.

What is a healthy BMI range?

A BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese. These ranges are the same for both men and women but may differ for children and older adults.

Is BMI an accurate measure of body fat?

BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, bone density, or fat distribution. Athletes with high muscle mass may have a high BMI without excess body fat. For a full health assessment, consult a healthcare professional.

How do I calculate BMI manually?

Metric: BMI = weight (kg) / height² (m). Imperial: BMI = (weight (lbs) × 703) / height² (inches). For example, a person who is 5'7" (170 cm) and weighs 150 lbs (68 kg): BMI = 68 / (1.70)² = 23.5.

Does BMI differ for men and women?

The BMI formula and categories are the same for men and women. However, women tend to have a higher body fat percentage than men at the same BMI. This is why some health professionals use waist circumference and body composition alongside BMI.

What BMI is considered obese?

A BMI of 30 or higher is classified as obese. Obesity is further divided into Class I (BMI 30–34.9), Class II (BMI 35–39.9), and Class III/Severe Obesity (BMI 40+).