To convert Celsius to Fahrenheit, a number that measures degrees of Celsius is needed. This number is usually designated by the letter C.
Multiply by nine, divide by five and then add 32. For example, to convert 20 degrees Celsius, first multiply 20 by nine to equal 180. Then divide 180 by five to equal 36. Then add 36 plus 32 to equal 68 degrees Fahrenheit.
Subtract 32, multiply by five and then divide by nine. For example, to convert 77 degrees Fahrenheit, first subtract 32 from 77 to equal 45. Then multiply 45 by five to equal 225. Then divide 225 by nine to equal 25 degrees Celsius.