Well Adam, yes and no. Do the arithmetic yourself; you'll find that your adding or subtracting 32 before or after multiplying or dividing by nine-fifths is much more difficult to remember and yet gives the same result as my easy-to-remember symmetric formula. My formula is based on a mathematic result, namely that when a domain is mapped into itself 1-to-1, there will be a fixed point. In the case of Franenheit and Celsius, that point is -40°. ________________________________ From: Adam Fikso <adam14113@ameritech.net> To: Pacific Bulb Society <pbs@lists.ibiblio.org> Sent: Monday, February 9, 2009 2:36:18 PM Subject: Re: [pbs] converting ºC to ºF or ºF to ºC ° David? Isn't the conversion formula supposed to be 5/9ths or 9/5ths + or - 32--not 40.? That's what I remember from Berkeley High School, and U of C. A little trick I learned in Hight School: Add 40º multiply by 5/9 or 9/5, depending upon which way you want to go Subtract 40º This rule is far easier to remember than any other.