One converter for the units that come up most often: length, weight, temperature, area, volume, speed, time, pressure, energy and digital storage. Pick a category, type a value, and every unit in that category updates at once so you can read off whichever you need.
Because the Celsius and Fahrenheit scales have different zero points, so conversion needs an offset as well as a multiplication: F = C x 9/5 + 32. Kelvin shares the Celsius degree size but starts at absolute zero.
No. A US gallon is 3.785 litres, an imperial gallon is 4.546 litres - about 20% larger. The same split applies to pints and fluid ounces, which is a frequent source of ruined recipes.
Both conventions exist. Storage manufacturers use 1000, operating systems often use 1024. The unambiguous binary units are KiB, MiB and GiB. This converter offers both.