BMI Calculator
Calculate your Body Mass Index with instant health insights
Measurement Unit
Calculate Your BMI
Body Mass Index (BMI) is a simple measure to assess if you have a healthy body weight for your height.
What is a BMI Calculator?
A BMI (Body Mass Index) calculator is a simple tool that estimates whether your weight is in a range often associated with better health, based on your height and weight. BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). It does not measure body fat directly, but it is widely used by health professionals and researchers as a quick screening indicator.
Our calculator lets you enter your height and weight (in metric or imperial units), then shows your BMI and a standard category (e.g. underweight, normal, overweight). It is for informational use only and is not a substitute for medical advice.
How It Works
The formula is:
BMI = weight (kg) ÷ height (m)²
If you enter height in centimetres and weight in kilograms, the tool converts and applies the formula. Some calculators also accept feet/inches and pounds and convert to metric before calculating. The result is a number (e.g. 22.5) that is then placed into a category.
Average Scores and BMI Categories Explained
BMI categories are based on ranges used by organisations such as the World Health Organization (WHO). Typical ranges for adults are:
- Under 18.5: Underweight
- 18.5 – 24.9: Normal (healthy weight) range
- 25 – 29.9: Overweight
- 30 and above: Often classified as obesity (sometimes with further bands, e.g. 30–34.9, 35+)
"Average" or "normal" in population terms often falls in the 18.5–24.9 band, but healthy ranges can vary by age, sex, and ethnicity. BMI does not distinguish muscle from fat, so very muscular people may fall in "overweight" without having excess body fat. Always interpret results with a healthcare provider.
Benefits of Using Our BMI Calculator
- Quick and free: Get your BMI in seconds with no account.
- Private: Your height and weight are not sent to our servers; calculation runs in your browser.
- Metric and imperial: Use kg/cm or lb/ft-in, depending on your preference.
- Clear categories: See which range your BMI falls into for general awareness.
- Educational: Helps you understand how BMI is calculated and used.
Improvement Tips (Health and Usage)
- Use consistent units and measure at a similar time of day for tracking over time.
- BMI is a screening tool, not a diagnosis. Discuss your results and goals with a doctor or dietitian.
- For fitness tracking, consider pairing with other metrics (e.g. waist circumference, activity level) rather than BMI alone.
- If you are working on weight or fitness, our Pomodoro timer can help structure workout or meal-prep sessions.
Frequently Asked Questions
Is the BMI calculator free?
Yes. The calculator is free to use with no registration.
Do you store my height or weight?
No. All inputs are used only in your browser to compute BMI. We don't collect or store your data.
Is BMI accurate for everyone?
BMI is a simple index and does not account for muscle mass, bone density, age, or ethnicity. It can be less accurate for athletes, older adults, and certain ethnic groups. A healthcare provider can give personalised advice.
Can children use this calculator?
Many BMI tools are designed for adults. Child and teen BMI is often interpreted using age- and sex-specific charts. If in doubt, use a paediatric calculator or ask a doctor.