How to use the unit converter

  1. Choose a category: length, weight, temperature, volume, area, speed, or data.
  2. Enter a value and choose the From and To units. The result updates immediately.
  3. Click ⇄ to swap the units.
  4. Below the converter, the same value is shown in every unit of the category, each with a Copy button.

Results are rounded to 10 significant digits. Very large and very small values are shown in scientific notation, for example 1.5e-7.

Exact conversion factors

The imperial and US units used here are defined exactly in terms of metric units by international agreement, so these conversions are exact rather than approximate:

  • 1 inch = 2.54 cm, so 1 foot = 0.3048 m and 1 mile = 1,609.344 m.
  • 1 pound = 0.45359237 kg, so 1 ounce = 28.349523125 g.
  • 1 US gallon = 3.785411784 liters. 1 UK (imperial) gallon = 4.54609 liters.
  • 1 nautical mile = 1,852 m, and 1 knot = 1 nautical mile per hour.
  • 1 acre = 4,046.8564224 m².

Temperature

Temperature conversions are not simple multiplications, because the scales start at different zero points:

  • °F = °C × 9/5 + 32
  • °C = (°F − 32) × 5/9
  • K = °C + 273.15

Useful reference points: water freezes at 0 °C (32 °F) and boils at 100 °C (212 °F) at sea level. −40 is the same in Celsius and Fahrenheit.

Data units: GB vs. GiB

Storage makers and most operating systems use different meanings of "gigabyte":

  • Decimal units (SI): 1 GB = 1,000,000,000 bytes. Drive manufacturers and macOS use these.
  • Binary units (IEC): 1 GiB = 1,073,741,824 bytes (1024³). Windows uses binary units but labels them "GB".

That is why a "1 TB" drive appears as about 931 GB in Windows: 1,000,000,000,000 bytes ÷ 1024³ ≈ 931.3. Nothing is missing; the two numbers measure the same space in different units.

US vs. UK volume

US and imperial (UK) units with the same name are different sizes. A US gallon is about 83% of a UK gallon, and a US fluid ounce (29.57 ml) is slightly larger than a UK fluid ounce (28.41 ml). The US customary units here are the ones used in American recipes and product labels. A US cup is the customary cup of 236.59 ml; nutrition labels use a rounded "legal cup" of 240 ml.

Frequently asked questions

Why do I see a long decimal like 3.280839895?

Most metric and imperial units do not divide evenly. One meter is exactly 1 ÷ 0.3048 feet, which is a repeating decimal. Round the result to the precision your work needs.

Is anything sent to a server?

No. All calculations happen in your browser.