BMI Calculator
Calculate your body mass index (BMI) online in seconds. Switch between metric (kg/cm) and imperial (lbs/ft-in), then see your category, BMI Prime, and a healthy weight range tailored to your height.
Calculate your BMI
Enter your details below. All calculations run in your browser — your data stays on your device.
BMI reference chart (WHO adults)
| Classification | BMI range | Your status |
|---|---|---|
| Underweight | Below 18.5 | — |
| Normal (healthy weight) | 18.5 – 24.9 | — |
| Overweight | 25 – 29.9 | — |
| Obesity | 30 or above | — |
BMI is a screening measure for adults and does not diagnose body fatness or health. Athletes and older adults may need different interpretations — speak with a qualified clinician for personal advice.
What is BMI and why use a BMI calculator?
Body mass index (BMI) is a simple ratio of weight to height squared, widely used as a quick screening tool for weight categories that may be linked to health risk. Our BMI calculator online helps you calculate BMI without spreadsheets: enter weight and height in metric or imperial units and see your number instantly alongside a clear BMI chart of standard WHO ranges.
How BMI is calculated
The formula is BMI = weight (kg) ÷ height (m)². If you use pounds and inches, we convert your entries to kilograms and metres first, then apply the same formula so your result matches clinical references.
BMI Prime
BMI Prime divides your BMI by 25 (the upper end of the “normal” range). A value around 1.0 means you are near that upper healthy threshold; values below 1 suggest lower BMI relative to that benchmark.
Healthy weight range
For a given height, the healthy weight calculator portion of this tool shows the weight range that corresponds to BMI 18.5–24.9 — often called a “normal” or healthy range for many adults. It is educational only and not a prescription.
- Fast, private calculations in your browser
- Metric and imperial support for global users
- Colour-coded gauge: underweight (blue), normal (green), overweight (orange), obese (red)
- Reference table aligned with common WHO adult categories
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