BMI Calculator
Body Mass Index calculator with metric and imperial support, plus health category.
What is the BMI Calculator?
The BMI Calculator returns your Body Mass Index, a widely used screening measure that relates weight to height. Enter your height and weight in metric or imperial units and the tool computes your BMI along with the category (underweight, healthy, overweight, obese) using the standard WHO ranges.
BMI is not a diagnosis but it is a useful starting point for a conversation with your doctor about weight-related risks such as diabetes, cardiovascular disease and joint issues. Millions of people check their BMI once or twice a year to track long-term trends.
The calculator runs entirely in your browser. Your height, weight and results never leave your device.
How to use the BMI Calculator
- 1Choose your preferred unit system: metric (cm/kg) or imperial (ft-in/lb).
- 2Enter your height.
- 3Enter your weight.
- 4Optionally add age and sex for a more nuanced insight.
- 5Read your BMI, category and healthy-weight range for your height.
- 6Adjust inputs to see how a target weight would move the BMI.
Key features
- Metric and imperial input
- Standard WHO categories (underweight, normal, overweight, obese)
- Healthy weight range for your height
- Adult (18+) and paediatric awareness disclaimer
- Runs offline
- Optional age/sex context
Examples
Example calculation
A person 175 cm tall weighing 72 kg has a BMI of 23.5 — squarely in the healthy range (18.5–24.9).
Overweight example
At 175 cm and 88 kg, BMI is 28.7, which lands in the overweight category (25–29.9).
Why use this tool
- Quick health screen you can repeat weekly
- Encourages awareness of weight trends
- Works with the units you are most comfortable with
- Private — nothing uploaded
- Free forever
Common use cases
- Personal health tracking
- Talking points before a doctor visit
- Setting realistic weight-loss or gain goals
- Teaching students about body composition
- Baseline before starting a fitness routine
Frequently asked questions
Is BMI accurate for athletes?
Not always. Muscle is denser than fat, so athletes can score "overweight" while being very fit.
Does it work for children?
BMI for children uses percentile charts, which this basic tool does not implement. Use paediatric charts for under-18s.
What BMI is healthy?
For adults, 18.5–24.9 is considered a healthy range by the WHO.
Is my data stored?
No — everything runs in your browser.
Should I only rely on BMI?
No. Combine BMI with waist circumference, blood pressure, cholesterol and lifestyle for a full picture.