BMI Calculator
Calculate your body mass index using height and weight. Switch between metric and imperial measurements, see your BMI on an adult reference scale, and understand what the result does—and does not—mean.
Calculate Your BMI
Enter your measurements below. Results are intended for adult screening, not diagnosis.
Your Measurements
Measurements are used for an on-page calculation. This calculator does not require an account.
Your BMI Result
Enter your height and weight, then select Calculate BMI to see your value and adult reference category.
What Is Body Mass Index (BMI)?
Body mass index (BMI) is a number calculated from a person’s weight and height. It is commonly used as a screening measure to classify weight relative to height in adults. It does not directly measure body fat or determine whether an individual is healthy.
Use your weight and height to estimate BMI.
Enter kilograms and centimetres or pounds and feet/inches.
Review commonly used adult BMI category thresholds.
How to Use the BMI Calculator
Choose Metric or Imperial, enter your measurements, and click Calculate BMI. Your result appears alongside an adult reference category. Change the numbers and calculate again, or select Reset to clear the inputs.
Adult BMI Categories
The following categories are commonly used for adults aged 20 and older. They are general screening categories and should not be used alone to assess an individual’s health.
| BMI | Adult category | Meaning |
|---|---|---|
| Below 18.5 | Underweight | Below the standard adult range |
| 18.5–24.9 | Healthy weight | Within the standard adult range |
| 25.0–29.9 | Overweight | Above the standard adult range |
| 30.0 or higher | Obesity | Within the standard adult obesity category |
For children and teenagers, BMI should be interpreted using age- and sex-specific growth references, not these adult cutoffs.
BMI Formula and Examples
Metric BMI Formula
BMI = weight (kg) ÷ [height (m)]². For example, 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) = approximately 22.9.
Imperial BMI Formula
BMI = 703 × weight (lb) ÷ [height (in)]². For example, 154 lb and 69 inches gives approximately 22.7. Small differences may arise from rounding and unit conversions.
What BMI Does Not Measure
BMI cannot distinguish muscle from fat or measure body-fat distribution, fitness, blood pressure, cholesterol or other aspects of health. People with higher muscle mass, older adults and pregnant individuals may need a more individualized assessment.
Using BMI Responsibly
BMI can help start a conversation about health, but it should not be treated as a diagnosis or a target that everyone must reach. Waist measurements, body composition, medical history and professional assessment can provide additional context.
Health disclaimer: This tool is for general information and education, not medical advice. It is not intended to assess children or teenagers, or to replace professional evaluation during pregnancy or for medical conditions. Speak with a qualified healthcare professional about concerns regarding weight or health.
Frequently Asked Questions
Is this BMI calculator free?
Yes. You can calculate BMI without signing up.
Can I calculate BMI using pounds and feet?
Yes. Select Imperial, then enter your weight in pounds and height in feet and additional inches.
Is BMI the same as body fat percentage?
No. BMI is calculated from height and weight, whereas body fat percentage estimates the proportion of body mass made up of fat.
Is BMI accurate for athletes?
BMI can be less informative for people with substantial muscle mass because it does not distinguish muscle from fat.
Does BMI apply to children?
Children and teenagers need age- and sex-specific BMI growth references; the adult categories on this page are not suitable.
Does a BMI in the healthy range guarantee good health?
No. BMI alone cannot assess overall health, fitness or disease risk.
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