BMI Calculator
Calculate body mass index using metric or US measurements.
Your inputs
Your inputs and files stay on your device.
Your result
A little input. A useful answer.
Enter your values and run the tool to see your result here.
How to use this tool
- Select units.
- Enter height and weight.
- Review BMI and category.
About BMI Calculator
BMI is a screening measure, not a medical diagnosis.
Does this tool send my data anywhere?
No. Its calculation or transformation happens on your device.
Using BMI Calculator with the right inputs
Calculate body mass index using metric or US measurements. Start by matching your task to the quantities and options shown below. The definitions of the inputs matter as much as the final number or transformed output; retain the original values so that you can repeat or check the result.
Inputs and options explained
- Measurement system: choose Metric · kg and cm, US · lb, feet and inches.
- Weight (kg): Enter the numeric value for this quantity using the units or scale shown in the label. The form indicates a minimum of 0.
- Height (cm): Use the measurement and unit named in the field. Do not substitute a diameter for a radius or mix unit scales. The form indicates a minimum of 0.
Method and interpretation
Body mass index is weight in kilograms divided by height in metres squared. In US mode, the tool converts pounds to kilograms and feet plus inches to metres before applying the same formula.
Worked example
For a weight of 70 kg and height of 175 cm, convert height to 1.75 m. BMI = 70 ÷ (1.75 × 1.75) = approximately 22.9 kg/m².
Assumptions and limitations
BMI is a screening measure and does not directly measure body fat or describe a person's overall health. Muscle mass and other individual factors affect interpretation. This page is not a diagnosis, a treatment plan or a weight-loss target. Children and teenagers need age- and sex-specific interpretation by an appropriate health professional.
Why does a small height error change the result?
Height is squared in the denominator. Use a measured height and the correct units rather than a rounded estimate; in US mode, enter whole feet and additional inches from zero to less than twelve.
Before you use the output
- Choose the intended action: Calculate BMI. Re-run the operation after changing an input or mode so that you are checking the updated result.
- Read the result label and any accompanying explanation. Keep the input values or source file with the output so that a later comparison uses the same assumptions.
- If a result looks unexpected, check units, separators and selected options first. Try a smaller example you can verify rather than repeatedly changing several settings at once.
Reference for further reading
CDC: About Body Mass Index. This reference explains the underlying topic; it does not certify this tool.
Questions or a result that needs checking?
If you find a discrepancy, report a problem with BMI Calculator. Include a non-sensitive example, the selected options, the result you expected and the result shown. This makes the issue easier to reproduce. See About & privacy for how the site handles tool inputs.