How the unit converter works

The unit converter turns a value in one unit into another unit of the same kind. Choose a category (length, weight, temperature, volume, area, speed, time, computing or data transfer), type the value, pick the source unit and the target unit, and press Calculate; the swap button exchanges the two units, and the table below the result shows the value in every unit of the category. It is useful in the kitchen and when traveling (cups, gallons, miles, km/h and mph), for school and engineering work, for boats and aircraft (knots, Mach), for comparing disk sizes with download speeds, and whenever a document uses units you are not used to.

In every category except temperature, each unit has a conversion factor to a base unit: the meter for length, the gram for weight, the meter per second for speed, the second for time and the bit for computing. The tool multiplies your value by the factor of the source unit to reach the base unit, then divides by the factor of the target unit. Metric prefixes such as micro, milli, kilo and mega are powers of ten, whereas the binary prefixes KiB, MiB and GiB are powers of 1,024. A knot is one nautical mile (exactly 1,852 m) per hour. Temperature is different because the scales have different zero points: it is an affine conversion that passes through kelvin, as in °F = °C × 9/5 + 32.

Example: 100 °C becomes 100 × 9/5 + 32 = 212 °F; 1 mile is 1,609.344 meters, because the inch is defined as exactly 25.4 mm and a mile has 63,360 inches; and 100 km/h is about 62.14 mph or 54 knots. Keep the limits in mind: results are rounded to a limited number of decimal places, a month and a year use average lengths (30.436875 and 365.25 days), US and imperial gallons, pints and cups are different volumes, 1 GB (10⁹ bytes) is not 1 GiB (2³⁰ bytes), and Mach uses the speed of sound at sea level in the standard atmosphere (340.294 m/s at 15 °C); at altitude sound is slower, so Mach 1 is a lower speed there. The results suit everyday use, not certified measurements.