This page is merely my own indulgence. I've often noticed that people don't seem to be able to judge the reasonableness of numbers when they read a research article or even critically examine the computer printouts, reports, or compare the reported results of one part of an analysis with results from another section. What follows here are some basic tricks of doing math in my head which I learned in grade school, but which don't seem to be taught much any more. I've attempted to organize these tricks somewhat and will add more as I'm able (or as people suggest additions).