How to use the BMI calculator
Choose a unit system, enter your weight and height, and press the button to see your result.
- 1Choose metric or imperial measurements.
- 2Enter your weight and height in the corresponding fields.
- 3Press “Calculate BMI” to see the value and category.
BMI guide
What does your body mass index mean?
Body mass index, or BMI, relates weight to height through a simple formula. It can be a starting point for interpreting an adult's weight, but one number does not tell the whole story.
How BMI is calculated
With the metric system, the formula is weight in kilograms divided by height in metres squared. For example, 70 kg and 1.75 m give a BMI of approximately 22.9.
If you use pounds, feet, and inches, the calculator converts height to inches and applies the imperial formula. The result is still expressed as BMI.
We display BMI to one decimal place, but assign its category using the full value. So a displayed result of 25.0 could still be in the healthy range if the unrounded value is below 25.
Categories and reference ranges
Underweight
Below 18.5.
Healthy range
From 18.5 to 24.9.
Overweight
From 25.0 to 29.9.
Class I obesity
From 30.0 to 34.9.
Class II obesity
From 35.0 to 39.9.
Class III obesity
40.0 or higher.
What it can and cannot tell you
BMI can help you notice a trend and decide whether it may be useful to review your habits or seek an assessment. It is more useful when you watch how it changes and compare it with other information.
- It does not distinguish muscle from fat.
- It does not show where body fat is concentrated.
- It does not use the same criteria for children and teenagers.
- It should not be interpreted in the same way during pregnancy.
How to interpret the result
A person with a lot of muscle mass may have a high BMI without having excess body fat. A BMI within the usual range can also hide other health factors. That is why the category is guidance, not a label.
Look at the trend
A sustained change often gives more context than a single measurement.
Add context
Waist size, body composition, age, and your overall health also matter.
Ask when needed
A professional can interpret the result alongside your history and goals.
A simple example
If someone weighs 80 kg and is 1.80 m tall, their BMI is approximately 24.7. The number is close to the upper limit of the reference range, so it is more useful to read it alongside the person's other information than to treat it as a final conclusion.
Important: how to interpret this result
This result is a mathematical calculation and is intended only as general guidance. It does not diagnose illness or determine on its own whether someone is healthy.
- This classification is intended for adults aged 20 and over.
- Do not use these categories for children or teenagers; their BMI is interpreted according to age and sex.
- If you have questions about your weight or health, ask a healthcare professional for an assessment.
The calculation happens in your browser
Weight and height are used locally to calculate the result. You do not need an account or to send that data to a calculation server.
Questions about the BMI calculator
What is the healthy BMI range?
In the standard adult classification, the reference range is usually between 18.5 and 24.9. It is general guidance, not a complete individual assessment.
Can I use pounds, feet, and inches?
Yes. Select “Imperial” and enter your weight in pounds and your height separately in feet and inches.
Does BMI work for everyone?
No. This classification is mainly intended as a reference for adults. It may be less representative for children, teenagers, pregnancy, and people with a lot of muscle mass.
Is my weight saved?
No. The calculation runs in your browser, and the page does not need to send your weight or height to a server.
This calculator provides general guidance. If you are concerned about your weight, health, or a recent change, consult a professional who can assess your full situation.