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Convert between metric and US standard units instantly — 8 categories covering length, weight, volume, area, speed, temperature, pressure, and time. All results update live as you type.
The metric system (SI) is used by most countries and is built on powers of ten — making conversions within the system straightforward (1 km = 1,000 m = 100,000 cm). US standard (customary) units are primarily used in the United States and include inches, feet, miles, pounds, ounces, gallons, and Fahrenheit. Converting between the two requires fixed conversion factors, such as 1 inch = 2.54 cm exactly.
Multiply kilometers by 0.621371 to get miles. For example, 10 km × 0.621371 = 6.214 miles. Select the Length category, choose Kilometers as your From Unit, and enter your value — the Miles result card updates instantly.
Multiply kilograms by 2.20462 to get pounds. For example, 70 kg × 2.20462 = 154.32 lbs. Select the Weight category and choose Kilograms as your From Unit.
Multiply liters by 0.264172 to get US gallons. For example, 10 L × 0.264172 = 2.642 US gal. Note that a US gallon equals 3.785 liters, while a UK imperial gallon equals 4.546 liters — this tool uses US gallons throughout.
The formula is: °F = (°C × 9/5) + 32. For example, 100°C = (100 × 1.8) + 32 = 212°F. This tool shows Celsius and Fahrenheit conversions. For all four scales including Kelvin and Rankine, visit the full Temperature Converter.
Three bonus length units hiding at the bottom of the Length dropdown. A Nautical Mile (nmi) equals exactly 1,852 meters — the international standard for maritime and aviation navigation, based on one minute of arc along Earth's surface. An Astronomical Unit (AU) equals approximately 1.496 × 10¹¹ meters — the average distance from the Earth to the Sun, and the standard unit for measuring distances within our solar system. Type 1 AU and watch the inch result remind you how small we are. A Light Year (ly) is the distance light travels in one year in a vacuum — approximately 9.461 × 10¹⁵ meters, or about 5.879 trillion miles. It is used by astronomers to measure distances between stars and galaxies. Type 1 meter into the converter and your light year result will be a number so small it needs scientific notation just to exist.
No. All conversions run entirely in your browser using JavaScript. No values are sent to any server, logged, or stored anywhere. Your data never leaves your device and disappears the moment you close the tab.