Free, fast, no-signup unit conversion tools
Ten converters covering the measurements that come up in everyday life, from recipes and road trips to tire pressure and file sizes. Results update as you type.
Length Converter
Convert between millimeters, meters, feet, miles, and more.
Weight & Mass Converter
Convert between milligrams, grams, kilograms, ounces, pounds, and tons.
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin.
Volume Converter
Convert between milliliters, liters, gallons, cups, and more.
Area Converter
Convert between square meters, square feet, acres, hectares, and more.
Speed Converter
Convert between mph, km/h, m/s, and knots.
Time Converter
Convert between seconds, minutes, hours, days, and years.
Digital Storage Converter
Convert between bits, bytes, KB, MB, GB, and TB.
Pressure Converter
Convert between pascals, bar, PSI, and atmospheres.
Energy Converter
Convert between joules, calories, watt-hours, and BTU.
Exact definitions, not rounded ones
Every converter uses the exact definitions behind each unit. An inch is defined as exactly 2.54 centimeters and a pound as exactly 0.45359237 kilograms, so conversions are only limited by ordinary floating-point arithmetic, not by a rounded factor copied from a table. Each converter page also has a quick-reference list of the most common values, handy when you just need a rough figure.
Several units share a name but not a size, which is where most conversion mistakes come from. A US gallon is smaller than a UK gallon, a US ton isn't a metric ton, and a gigabyte on a drive label isn't the same as the gigabyte Windows reports. The converters label which version they use (US gallons, US tons, metric tons, and 1,024-based storage units), and the guides explain where the differences came from.
Guides
All guides →Aug 17, 2026
Metric vs. imperial: a practical conversion cheat sheet
The handful of conversions people actually look up constantly, plus a few memorable approximation tricks for doing them in your head.
Aug 10, 2026
Why converting Celsius to Fahrenheit isn't just multiply-and-add
Most unit conversions are a single multiplier. Temperature needs an offset too, because Celsius and Fahrenheit don't share a zero point. The formulas, the common mistake, and why science uses Kelvin.
Aug 14, 2026
KB vs KiB vs MB: why your hard drive shows less space than advertised
Drive manufacturers count in decimal (1,000-based) units; your operating system counts in binary (1,024-based) units. Here's the actual math behind the missing gigabytes.
Aug 26, 2026
US gallons vs UK gallons: why they're not the same size
A UK gallon is about 20% bigger than a US gallon, and they've never matched. Here's the actual reason, plus why US and UK cups and fluid ounces are also different.