Rule of thumb

The phrase "rule of thumb" means a practical and approximate way of doing or measuring something based on experience and common sense rather than theory or strict scientific accuracy. It is a general guideline or helpful hint that provides simplified advice on how to do something in most situations. The origin of the phrase comes from the use of the thumb's width as a rough measurement in trades like textiles, dating back to the 1600s.

It is used when explaining an overarching rule or principle derived from experience. It is not a precise or step-by-step rule but rather a rough estimate or general practice to follow.

As a rule of thumb, the ice on the lake should be at least two inches thick to support one person.

A good rule of thumb is that a portion of rice is two handfuls.

A rule of thumb is a rough guideline and not always accurate.

This rule of thumb generally works, but there are exceptions.

The rule of thumb is useful for quick estimates but not reliable in every situation.