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

Genna Contino shared a rule of thumb that can help you manage this risk automatically.

From MarketWatch ● Jun. 26, 2026

A common rule of thumb says to buy builders at one-times book value and sell at two-times.

From Barron's ● Jun. 1, 2026

My rule of thumb is to add one cup of cottage cheese for every cup of sauce.

From Salon ● May 24, 2026

“The rule of thumb I use with clients is six months liquid, minimum, and that number goes up if you’re carrying financial responsibility for adult children or aging parents.”

From MarketWatch ● May 14, 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