What Is BMI?
BMI stands for Body Mass Index. It is a commonly used screening measurement that compares a person's weight with their height. BMI can help classify adult weight into general categories such as underweight, healthy weight, overweight and obesity.
Our free BMI Calculator makes it easy to calculate BMI online using either metric measurements such as kilograms and centimeters or imperial measurements such as pounds, feet and inches.
BMI Categories for Adults
The standard adult BMI categories are generally:
- Underweight: BMI below 18.5
- Healthy weight: BMI from 18.5 to 24.9
- Overweight: BMI from 25.0 to 29.9
- Obesity: BMI 30.0 or higher
These ranges are general screening categories and do not provide a complete assessment of an individual's health.
How to Calculate BMI
For metric measurements, BMI is calculated by dividing weight in kilograms by height in meters squared.
BMI = weight (kg) ÷ height² (m²)
For example, a person weighing 70 kg and measuring 1.75 meters tall would have a BMI of approximately 22.9.
Using Imperial Measurements
When using pounds and inches, the standard BMI calculation uses the person's weight in pounds and height in inches.
The calculator automatically performs the required conversion, so you do not need to calculate it manually.
Healthy Weight Range
For adults, a BMI between 18.5 and 24.9 is commonly considered the healthy or normal weight range. However, the appropriate weight for an individual can vary depending on factors such as age, muscle mass, body composition and overall health.
BMI should therefore be considered a screening measurement rather than a diagnostic tool.
Is BMI Accurate?
BMI is useful because it is simple, inexpensive and easy to calculate. However, it does not directly measure body fat or distinguish between muscle and fat.
For example, athletes and people with high muscle mass may have a higher BMI even though they have relatively low body fat.
For a more complete assessment, healthcare professionals may consider other measurements such as waist circumference, body composition, medical history and lifestyle factors.
Frequently Asked Questions
What is BMI?
BMI, or Body Mass Index, is a numerical measurement based on height and weight that is commonly used to classify general adult weight categories.
How is BMI calculated?
BMI is calculated by dividing weight in kilograms by height in meters squared. The calculator automatically handles the conversion when imperial units are used.
What is a healthy BMI range?
For most adults, a BMI from 18.5 to 24.9 is generally classified as the healthy or normal weight range.
Can I calculate BMI using pounds and inches?
Yes. Select the Imperial option and enter your height in feet and inches and your weight in pounds.
Is BMI the same for men and women?
The standard adult BMI categories are generally the same for men and women. However, BMI does not account for differences in muscle mass or body composition.
Does BMI measure body fat?
No. BMI does not directly measure body fat. It only uses height and weight, which means it cannot distinguish between muscle and fat.
What BMI is considered overweight?
For adults, a BMI between 25.0 and 29.9 is commonly classified as overweight.
What BMI is considered obese?
For adults, a BMI of 30.0 or higher is commonly classified as obesity.