The term rule of thumb refers to heuristic.
A heuristic is a mental shortcut that allows people to make judgments efficiently and quickly.
The word heuristic comes from Greek <em>find or discover.</em>
It a an approach to problem solving that uses a practical, rational or logical method. This method may not always be correct, but it's sufficient to reach an immediate goal.
Some examples of heuristic are: the rule of thumb, an educated guess, common sense or an intuitive judgement.
<em>The rule of thumb refers to a procedure or standard based on practical experience rather than theory. </em>