I would think that posting a link to one of the conversion sites would be sufficient. Post it perhaps in "Goodies".
For inches to centimeters I find it easy enough to remember "2.5" for a pretty close estimate. Multiply inches by 2.5 to get centimeters.
As Sue said temperature is a more complex calculation; a link to a conversion site would be useful and handy. Same with money conversions as some of us do international orders.
Of course I have a conversion site bookmarked but I almost always use it for ATP purposes. Having it onsite here would be more convenient I would think.
