rule of thumb

American  

noun

1. a general or approximate principle, procedure, or rule based on experience or practice, as opposed to a specific, scientific calculation or estimate.

2. a rough, practical method of procedure.

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rule of thumb British  

noun

1. 1. a rough and practical approach, based on experience, rather than a scientific or precise one based on theory

   2. ( as modifier )

      a rule-of-thumb decision

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rule of thumb Cultural  

1. A practical principle that comes from the wisdom of experience and is usually but not always valid: “When playing baseball, a good rule of thumb is to put your best hitter fourth in the batting order.”

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rule of thumb Idioms  

1. A rough and useful principle or method, based on experience rather than precisely accurate measures. For example, His work with the youth group is largely by rule of thumb. This expression alludes to making rough estimates of measurements by using one's thumb. [Second half of 1600s]

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Etymology

Origin of rule of thumb

First recorded in 1685–95

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Example Sentences

See Examples For:

rule of thumb

A financial rule of thumb tells us to ignore the worrywarts who say American stocks are expensive.

From The Wall Street Journal ● Nov. 2, 2026

Here’s a simple rule of thumb for assessing all these claims: None of them is true.

From Los Angeles Times ● Oct. 6, 2026

A basic rule of thumb is that to be ultra-processed a product needs more than five ingredients, with at least one not normally found in your kitchen - things like emulsifiers, additives and flavourings.

From BBC ● Sep. 26, 2026

The closest thing to a rule of thumb holds that courts should apply the rules of the state that has the most significant relationship to the case.

From Slate ● Aug. 28, 2026

“The rule of thumb is that you buy at ten and sell at twenty.”

From "The Big Short" by Michael Lewis

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