Want to check your Body Mass Index quickly? Our free BMI Calculator helps you calculate your BMI using your height and weight. Enter your details, choose your preferred units, and get your BMI result instantly.
The calculator also shows the standard BMI category associated with your result, such as underweight, healthy weight, overweight, or obesity. You can use it for a quick general check of your weight in relation to your height.
BMI is only a screening measure and does not directly measure body fat or overall health. Factors such as muscle mass, age, sex, and other individual characteristics can affect how a BMI result should be interpreted.
What Is a BMI Calculator?
A BMI Calculator is a simple tool that uses your height and weight to calculate your Body Mass Index (BMI). BMI is a number that can be used as a general screening measure for weight in relation to height.
The result is usually placed into a standard BMI category. For adults, these categories are commonly described as underweight, healthy weight, overweight, and obesity.
BMI is useful as a quick starting point, but it does not tell you everything about your health or body composition.
How to Use the BMI Calculator
Using the calculator takes only a few steps:
- Choose Metric (kg, cm) or Imperial (lb, in).
- Enter your weight.
- Enter your height.
- Click Calculate.
- Your BMI and BMI category will appear instantly.
You can use the Clear button to start again with new values.
How Is BMI Calculated?
For metric measurements, BMI is calculated using:
BMI = Weight (kg) ÷ Height² (m)
For example, if someone weighs 70 kg and is 175 cm tall:
BMI = 70 ÷ (1.75 × 1.75) = 22.9
The calculator handles the conversion and calculation automatically.
For imperial measurements, the calculation uses weight in pounds and height in inches.
Adult BMI Categories
For adults, the standard BMI categories are:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25.0–29.9 | Overweight |
| 30.0 or higher | Obesity |
These ranges are commonly used for adult BMI screening. BMI categories should not be treated as a diagnosis by themselves.
BMI Calculator for kg and cm
If you normally use the metric system, select Metric (kg, cm).
Enter your weight in kilograms and height in centimetres. The calculator converts the height to metres automatically before calculating your BMI.
For example, a person weighing 75 kg and measuring 180 cm would have a BMI of about 23.1.
BMI Calculator for lb and inches
If you use pounds and inches, select Imperial (lb, in).
Enter your weight in pounds and height in inches. The calculator uses the imperial BMI formula automatically.
This is useful if your height and weight are already recorded in US customary units.
What Does a BMI Number Mean?
BMI provides a general indication of how your weight compares with your height.
A BMI below 18.5 falls into the underweight category, while 18.5 to 24.9 is generally classified as healthy weight. A BMI from 25 to 29.9 is classified as overweight, and a BMI of 30 or above falls into the obesity category.
These categories are useful for screening large groups of people, but they do not describe every individual accurately.
Is BMI the Same as Body Fat?
No. BMI and body fat are different measurements.
BMI uses only height and weight. It does not directly measure how much of your body weight comes from fat, muscle, bone, or other tissues.
For example, someone with a lot of muscle may have a higher BMI without having a high amount of body fat.
Other information, such as waist measurement and body composition, can provide additional context.
BMI for Men and Women
The standard adult BMI calculation itself does not use different formulas for men and women.
However, BMI should be interpreted alongside other factors, including age, sex, muscle mass, and overall health.
Is BMI Suitable for Everyone?
Standard adult BMI categories are not intended to be used in exactly the same way for every person.
Children and teenagers, for example, are generally assessed using age- and sex-specific BMI measurements rather than the standard adult categories.
BMI can also be less useful for people with unusually high muscle mass, certain medical conditions, or other factors that affect body composition.
BMI and Age
BMI does not directly include age in its calculation. The same height and weight will produce the same BMI regardless of age.
However, age can be important when interpreting BMI and assessing overall health.
For children and teenagers, BMI is interpreted differently using growth charts and age-specific information.
What Is a Healthy BMI?
For adults, a BMI from 18.5 to 24.9 is generally classified as the healthy-weight range.
However, being within this range does not automatically mean that a person is healthy, and being outside it does not automatically mean that someone is unhealthy.
BMI should be viewed as one piece of information rather than a complete measure of health.
Frequently Asked Questions
What is a normal BMI?
For adults, a BMI from 18.5 to 24.9 is generally classified as the healthy-weight range.
Is a BMI of 25 overweight?
Under standard adult BMI categories, a BMI of 25.0 or higher falls into the overweight category.
Is BMI accurate?
BMI can be useful as a general screening measure, but it has limitations because it does not directly measure body fat or body composition.
Can I calculate BMI in pounds and inches?
Yes. Select Imperial (lb, in) and enter your weight in pounds and height in inches.
Can I calculate BMI in kilograms and centimetres?
Yes. Select Metric (kg, cm) and enter your weight in kilograms and height in centimetres.
Does BMI account for muscle?
No. BMI does not directly distinguish between muscle, fat, bone, and other tissues.
Is BMI different for men and women?
The standard adult BMI formula is the same, but BMI may be interpreted alongside sex and other personal factors.
Can children use this BMI calculator?
This calculator uses standard adult BMI categories. Children and teenagers require age- and sex-specific BMI interpretation.
Disclaimer: This BMI Calculator is provided for general informational purposes only. BMI is a screening measure and does not directly measure body fat or provide a complete assessment of health. Individual results can vary depending on factors such as age, sex, muscle mass, body composition, and other health factors. For personal health concerns or medical decisions, consider speaking with a qualified healthcare professional.