What is the BMI Calculator?
For adults, BMI below 18.5 is underweight; 18.5 to below 25 is healthy; 25 to below 30 is overweight; and 30 or more is obesity range.
The Calcwise BMI tool is designed to give a fast answer while keeping the arithmetic visible. Enter the requested values, check the units, and the result updates in your browser. Your calculator entries are not sent to a Calcwise server.
Choose the measurement system you use
The interactive calculator supports Metric, US customary and Imperial (UK) measurements where physical units matter. Choose the system above the form and Calcwise converts your entries internally before applying the same formula.
Your unit preference is remembered in this browser. Shared calculator links also keep the selected unit system so another person sees the values in the same units.
How to use this calculator
- Enter values using the units shown beside each field. In the interactive calculator, each field also shows a plain-language example or meaning guide.
- Check that the values describe the same period or situation where relevant.
- Read the main result and the supporting figures shown beside it.
- Use the reset button to return to the example values.
Inputs used
- Weight — In kilograms
- Height — In centimetres
BMI Calculator formula
The formula is shown so you can understand the relationship between the inputs instead of treating the result as a black box.
Worked example
70 kg and 175 cm gives a BMI of 22.86, in the healthy range.
Your own result may differ because it uses the exact values you enter. For comparisons, keep the method and units consistent from one calculation to the next.
Important assumptions and limitations
For adult information only. BMI is a screening measure, not a diagnosis or a complete picture of health.
Calculator outputs are estimates unless the underlying arithmetic is exact by definition. For decisions involving tax filing, lending, health, contracts or institutional grading rules, use the calculator as a first check and confirm the final decision with the relevant authoritative source.
Frequently asked questions
What does the BMI Calculator calculate?
For adults, BMI below 18.5 is underweight; 18.5 to below 25 is healthy; 25 to below 30 is overweight; and 30 or more is obesity range.
What formula does the BMI Calculator use?
BMI = weight in kilograms ÷ (height in metres)²
Is the BMI Calculator result exact?
For adult information only. BMI is a screening measure, not a diagnosis or a complete picture of health.
How should I use the BMI Calculator result?
Use the result as a practical estimate or planning check. Keep the inputs consistent, read the assumptions on this page, and verify important financial, academic or health decisions with the appropriate official or professional source when needed.
Pro mode: Measurement uncertainty
See how a small weight/height measurement uncertainty can shift the BMI estimate.
Enable Pro mode above the input form to reveal the advanced scenario fields. The normal result stays visible, and a separate Pro analysis appears underneath so you can compare the basic answer with the deeper model.
Advanced options
- Possible weight error (kg)
- Possible height error (cm)