BMI Calculator - Free Body Mass Index Calculator

What is Body Mass Index (BMI)?

Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults. It is calculated by dividing your weight in kilograms by the square of your height in meters.

Adult BMI Categories

Underweight: BMI less than 18.5
Normal weight: BMI 18.5 to 24.9
Overweight: BMI 25 to 29.9
Obese: BMI 30 or greater

Limitations of BMI

While BMI is a useful, inexpensive, and quick method for identifying potential weight problems in populations, it does have limitations for individuals. Because it only relies on height and weight, it does not distinguish between weight from fat and weight from muscle. Therefore, highly muscular athletes may have a high BMI but a low percentage of body fat.

Frequently Asked Questions

What is BMI?

BMI stands for Body Mass Index. It is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m².

How accurate is the BMI calculator?

BMI is a useful screening tool for the general population but does not directly measure body fat. It can overestimate adiposity in highly muscular individuals (like athletes) and underestimate it in older persons who have lost muscle mass.

What are the adult BMI categories?

According to the WHO, the standard weight status categories associated with BMI ranges for adults are: Underweight (< 18.5), Normal weight (18.5 - 24.9), Overweight (25 - 29.9), and Obese (30 or greater).

Is BMI the same for men and women?

Yes, the basic BMI calculation and the standard weight status categories (underweight, normal, overweight, obese) are the same for adult men and women of all body types and ages.