Why we would 32 in Celsius to Fahrenheit & Vice Versa. Please!!!! Hey fellows , please tell me why we add 32 to celsius to fahrenheit conversion and vice versa. According to my mind I derive C to F formula of my own. I do following. 1)I look and choose same scale of F and C . The most obvious of which is freezing and boiling point. For F (32-212) and for C (0-100). 2)Now to derive formula for C to F , i divided 180/100 =1.8 it means that if celsius then corresponding F is 1.8. So I now want to know how much is 37C in Fahrenheit then I multiplied it by 1.8*37=66.6 which is not true unless I add 32 to this. But why would I actually do that. Please explain.