text: what is the difference between celsius and fahrenheit grades? how can you convert fahrenheit to celsius and viceversa they're different units of measurement, almost like inches and centimeters. to go from celsius to fahrenheit, multiply by 1.8 and add 32. to go from fahrenheit to celsius, subtract 32 and multiply by 5/9.  and, uh, that hot and smart girl? one, that's a cartoon, and two, what she said is wrong...