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

Example Sentences

See Examples For:

rule of thumb

"Always ask, would you put the same thing in an email?" he says, as a rule of thumb.

From BBC ● Aug. 17, 2026

If you feel compelled to comment on a famous woman’s body, a good rule of thumb to remember is “don’t.”

From Slate ● Aug. 6, 2026

If Yale had been treated like an individual investor, Ang’s rule of thumb suggests that Swensen’s epic return would have been slashed to about 8.7% annually after tax.

From The Wall Street Journal ● Jul. 31, 2026

The production’s rule of thumb became trying to execute scenes practically, in front of a lens, wherever possible.

From Los Angeles Times ● Jul. 30, 2026

This looks to us like a principle, maxim, or rule of thumb, not a law, because it lacks specificity.

From "The Invention of Science" by David Wootton

Related Words

• criterion