Rules of Thumb.Org. ‘A rule of thumb is a homemade recipe for making a guess. It is an easy-to-remember guide that falls somewhere between a mathematical formula and a shot in the dark. A farmer, for instance, knows to plant his corn when oak leaves are the size of squirrels’ ears. An economics professor knows from sad experience that inviting more than 25 percent of the guests for a university dinner party from the economics department ruins the conversation. Rules of thumb are a kind of tool. They help you appraise a problem or situation. They make it easier to consider the subtleties of the topic at hand; they give you a feel for a subject.
A rule of thumb turns information you have into information you need. The goal of this website is to gather every rule of thumb on earth into one gargantuan, easily searchable online reference database that will be accessible from anywhere in the world and continue to grow forever.’