Unit converter

How to convert a measurement

Select a measurement type, enter the value, and choose the starting and destination units. Swap units reverses the unit choices while keeping the entered number. Length, mass, area, and volume conversions multiply through a common base unit. Temperature conversions also apply an offset.

Worked examples

Illustrative examples: 12 inches × 0.0254 meters per inch = 0.3048 meters = 30.48 centimeters. One US liquid gallon is 3.785411784 liters. To convert 68 °F, subtract 32, multiply by 5, and divide by 9: the result is 20 °C. The displayed answer uses up to ten significant digits; internal arithmetic uses the unrounded stored factors.

Pick the right kind of unit

An ounce of mass and a fluid ounce measure different quantities. This converter cannot turn volume into mass without a material density, so those units appear in separate groups. Mass uses the avoirdupois pound and ounce, not troy units. Volume uses US customary liquid measures, not Imperial or US dry measures. A US customary cup here is 236.5882365 mL; do not substitute it for a nutrition-label metric cup.

Precision and practical limits

An exact conversion factor does not make a measurement exact. Preserve appropriate significant figures for the original reading. Temperature inputs below absolute zero are rejected. Negative values in other groups are allowed for mathematical differences, but physical quantities such as package mass ordinarily require a nonnegative value. The factors follow NIST's SI conversion reference; survey-foot and historical units are outside this tool's scope.