Enter your weight and height (metric or imperial), and the BMI and category update as you type.
Switch the unit dropdown between metric and imperial at any point - the weight and height labels relabel to kg/cm or lb/in automatically, and both fields keep their values.
If the height field is left at zero, the tool asks for a height greater than zero instead of showing a BMI result.
BMI Calculator
Calculate body mass index (BMI) from height and weight and see the standard weight category. Use it as a quick, general reference point for weight-for-height.
Key features
- Metric or imperial units: pick kg/cm or lb/in from the unit dropdown and the weight and height labels switch to match, so there is no unit conversion to do by hand.
- Instant weight category: BMI sorts into four standard bands - Underweight (below 18.5), Normal weight (18.5 to 25), Overweight (25 to 30), and Obesity (30 and above) - and the category updates alongside the BMI value as you type.
- Stays on your device: the height and weight you enter stay in the browser; BMI is worked out on this device, with no upload and no account.
- Guided input, values kept: switch the unit dropdown at any point and both the weight and height you already typed stay in place - only the labels change to kg/cm or lb/in. Leave the height at zero and the tool prompts for a height greater than zero instead of showing a misleading number, and the BMI itself is rounded to one decimal place.
What BMI does not tell you
BMI does not account for muscle mass, age, or body composition - it is a general screening estimate only, not medical advice.
This tool, a health app, or an upload-based service
Three routes cover the same job, and they differ on where the numbers go and what you have to install.
| Aspect | BMI Calculator (this tool) | Health/fitness app | Upload-based online service |
|---|---|---|---|
| Where your data goes | Stays on this device | Stays on this device | Uploaded to a server |
| Install required | No | Yes | No |
| Works without an account | Yes | Varies by app | Varies by service |
| Works offline | No - needs the initial page load | Yes, after install | No |
Reach for this page for a one-off check, or to compare BMI before and after a weight change. An app is the better fit when you want BMI tracked over time next to other health metrics.
Not sure this is the right check for what you need right now? See when to use the BMI calculator.
Frequently Asked Questions
What does BMI Calculator do?
Calculate body mass index (BMI) from height and weight and see the standard weight category.
When should I reach for bmi calculator?
Use it as a quick, general reference point for weight-for-height.
What complementary tools work well alongside bmi calculator?
BMI does not account for muscle mass, age, or body composition - it is a general screening estimate only.