Unit Conversions
Instant, accurate conversions โ length, weight, temperature, data & more.
About unit conversions
Direct unit conversions across length, weight, temperature, volume, area, speed, time and digital storage โ each with its own page showing the exact conversion factor rather than only the answer.
Showing the factor is deliberate. A converter that returns a number teaches you nothing and has to be revisited every time; one that shows 1 inch = 2.54 cm gives you something you can carry. That particular figure is worth remembering because it is exact by definition โ the inch was formally defined as precisely 2.54 centimetres by international agreement in 1959, so it is not a rounded approximation.
Temperature is the exception to how everything else here works. Length, weight and volume conversions are single multiplications because their scales share a zero point: zero metres is zero feet. Temperature scales do not. Zero Celsius is 32 Fahrenheit, so converting requires both a multiplication and an offset โ multiply by 9/5, then add 32. This is also why a temperature difference converts differently from a temperature: a rise of 10ยฐC is a rise of 18ยฐF, not 50ยฐF.
For cooking conversions specifically, be careful with volume. A US cup is 236.6 ml, a metric cup is 250 ml, and an imperial cup is 284 ml. Recipes rarely state which they mean, and in baking the difference is enough to matter.
Frequently asked questions
Why does temperature conversion need a formula instead of a factor?
Because Celsius and Fahrenheit do not share a zero point. Scales that start from the same zero โ metres and feet, kilograms and pounds โ convert with a single multiplication. Zero Celsius is 32 Fahrenheit, so the conversion needs both a multiplier (9/5) and an offset (+32).
Is 1 inch exactly 2.54 cm or rounded?
Exactly. The international yard and pound agreement of 1959 defined the inch as precisely 2.54 centimetres, so it is a definition rather than a measurement. Many other imperial-to-metric factors are similarly exact by definition.
Which cup measurement do recipes mean?
It depends on origin, and recipes rarely say. A US customary cup is 236.6 ml, a metric cup is 250 ml, and an imperial cup is 284 ml. For baking, where ratios matter, weighing ingredients in grams avoids the problem entirely and is more accurate regardless.
Is a kilobyte 1000 or 1024 bytes?
Both conventions are in use, which is why file sizes appear to disagree between operating systems. The SI definition is 1000 bytes; the binary convention used by much software is 1024, properly called a kibibyte (KiB). Storage manufacturers use 1000, which is why a advertised 1 TB drive shows as roughly 931 GB in an operating system counting in binary.