If you are not keen on doing division or multiplication in your head, another quick trick for C to F conversion is by adding 18F degrees for every 10C. Zero starts at 32. So for 10 degrees C, its 32+18 = 50F. 30C = 32+18+18+18 = 86F, etc. I always remember that 20C is 68F because that's the temperature in my office most of winter! Its just as essay to remember that for every 5C, you add 9F and for every 3C you add 5F (5.4 actual) and every 1C you add 2F (1.8 actual). You can quickly and easily arrive at an accurate estimate of temperature. Converting back to C is just the opposite.