Until Earth establishes a universal Federation and unites all nations and planets under a single banner, we'll probably keep wrestling with converting between different standards of measurement. Fortunately, one of the most common—converting between Fahrenheit and Celsius—is also pretty easy to calculate.
Celsius to Fahrenheit: Multiply the temperature by 2, then add 30.
Fahrenheit to Celsius: Subtract 30, then divide by 2.
This is more of a ballpark estimate, but for most things, it will work alright. If you do need to get more specific, however, replace 2 with 1.8 and replace 30 with 32 in the above equations.