Unit Converter

Values are converted through the category's base unit. Temperature needs an offset as well as a scale: °F = °C × 9/5 + 32.

1 inch = exactly 2.54 centimeters; 1 pound = exactly 0.45359237 kilograms. 20°C = 68°F, not 36°F.

Check the measurement category and units before copying the output. US and imperial gallons are different units; do not substitute one for the other.

Displayed decimals are rounded. For regulated engineering, medicine or trade, confirm the required precision and applicable unit standard independently.

Start by choosing length, weight or mass, or temperature from the available categories. Then choose the source unit, destination unit and value. The result describes the same quantity in a different unit; it does not create a measurement that was more accurate than the original. Confirm the direction before copying the output. Converting centimeters to inches is not the same numerical operation as converting inches to centimeters, even though both use the same defined relationship.

For length and mass, the tool converts through a common base unit. Temperature is handled separately because it needs an offset as well as a scaling factor. The form does not convert money, clothing sizes or arbitrary units from a manufacturer's chart. If the measurement type or exact unit you need is not in the available choices, use a suitable reference rather than selecting something that merely sounds similar.

One inch is exactly 2.54 centimeters, so ten inches gives 25.4 centimeters. Reversing the direction, 25.4 centimeters gives ten inches. One pound is exactly 0.45359237 kilograms; the displayed result may show fewer digits because of formatting. These defined relationships make good sanity checks for the direction of a conversion. If ten inches appears as a very small fraction of a centimeter, the selected source and destination units are probably not the intended pair.

A decimal measurement is not automatically a compound measurement. Five feet nine inches is 5.75 feet because nine divided by 12 is 0.75. Entering 5.9 feet describes a different length. Likewise, a scale reading that shows pounds and remaining ounces needs to be expressed as a single numerical value in the selected unit. The converter does not parse a phrase containing several units into one measurement for you.

Celsius and Fahrenheit have different zero points. Zero degrees Celsius converts to 32 degrees Fahrenheit, and 20 degrees Celsius converts to 68 degrees Fahrenheit. Multiplying 20 by 9/5 gives 36, but without adding 32 that is not the Fahrenheit temperature. The reverse operation subtracts 32 before multiplying by 5/9. Keeping the offset in the calculation is essential even when a quick mental estimate seems close.

There is also a distinction between a temperature reading and a temperature difference. A rise of ten Celsius degrees corresponds to a rise of 18 Fahrenheit degrees, not a Fahrenheit reading of 50. This form converts absolute readings using the scale offset. If you are converting a change or tolerance, use the scale factor appropriate to a difference rather than treating the output for an absolute reading as the answer.

The displayed digits reflect formatting, not the certainty of your original measurement. A length measured only to the nearest inch does not become known to tiny fractions of a centimeter after conversion. Keep enough digits for the task, but do not mistake a long decimal for improved measurement quality. Rounding an intermediate result before converting it again can also introduce a small difference, so retain the original input when practical.

For engineering, medicine, regulated trade or a specification with a stated tolerance, confirm the applicable unit standard and precision independently. Some names refer to different units in different systems; US and imperial gallons, for example, are not interchangeable. Those volume conversions are not offered in this form. The NIST reference provides wider context, but this page remains a calculator for the choices actually shown, not a substitute for checking an ambiguous unit on a document.