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Click a row to make it the target unit. Values are rounded to the chosen significant figures for display only.
Convert length, weight, temperature, volume, area, speed, data, pressure, energy, and time, and see the value in every unit of the category at once.
| Unit | Value |
|---|
Click a row to make it the target unit. Values are rounded to the chosen significant figures for display only.
This unit converter covers the ten categories people convert most: length, weight and mass, temperature, volume (both US and UK imperial measures), area, speed, digital storage (decimal SI and binary IEC prefixes), pressure, energy, and time. Enter a value, pick the unit it is in, and the page shows the result in your target unit and, below it, in every other unit of that category, so you can compare a kilogram against pounds, ounces, stones, and grains without running the tool ten times. A swap button reverses the direction, a precision setting controls significant figures, and the URL updates so you can bookmark or share a specific conversion. It is for cooks, travelers, students, engineers, and anyone reading a spec sheet or recipe written in the wrong units.
Every unit is defined by an exact factor to a base unit (meter, kilogram, liter, square meter, meter per second, byte, pascal, joule, second), so converting from A to B is value × factor(A) ÷ factor(B), a single multiplication and division with no chained rounding. Factors come from the international definitions: the inch is exactly 0.0254 m (so the mile is 1,609.344 m), the pound is exactly 0.45359237 kg, the US gallon is 231 cubic inches = 3.785411784 L, the UK gallon is 4.54609 L, the acre is 4,046.8564224 m², the standard atmosphere is 101,325 Pa, the BTU (International Table) is 1,055.05585262 J, and the calorie is the thermochemical 4.184 J. Temperature is the one affine category: values pass through kelvin using K = °C + 273.15, K = (°F + 459.67) × 5/9, and K = °R × 5/9. Results are rounded only at display time to the number of significant figures you choose.
A gigabyte (GB) is 10^9 = 1,000,000,000 bytes under the SI decimal prefixes, which is how drive manufacturers and network speeds are quoted. A gibibyte (GiB) is 2^30 = 1,073,741,824 bytes, the binary prefix defined by the IEC. Windows reports sizes in binary units but labels them GB, which is why a 500 GB drive shows as about 465 GB. This converter lists both families so you can see the 7.4% gap directly.
The two systems diverged in 1824 when Britain redefined its gallon as the volume of 10 pounds of water (4.54609 L), while the United States kept the older wine gallon of 231 cubic inches (3.785411784 L). A UK pint is 20 UK fluid ounces (568 mL) and a US pint is 16 US fluid ounces (473 mL); the fluid ounces themselves differ by about 4%. Recipes and beer measures therefore need the right variant, which is why both are listed.
Most are exact by definition: the inch, foot, yard, and mile since the 1959 international agreement; the pound since 1959 as well; the US gallon by its 231 cubic inch definition; the calorie, BTU, kilowatt-hour, and atmosphere by convention. A few are measured constants rounded to the precision given, notably the psi (6,894.757293168 Pa, itself derived from exact definitions), the electronvolt (1.602176634 × 10^-19 J, exact since 2019), and the knot (1,852 m per hour, exact). Rounding happens only when displaying.
There is no single length for a month or year, so the converter uses averages: a mean Gregorian year of 365.2425 days (31,556,952 seconds), which is the calendar's long-run average including leap years, and one twelfth of that, 30.436875 days, for a month. For an exact number of days between two dates, use a date calculator instead; these averages are for converting rates and durations such as seconds per year.
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