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

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

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

“My rule of thumb for everything in this movie,” he said, “we have to give the audience reasons to believe.”

From The Wall Street Journal ● Jul. 20, 2026

As a rule of thumb, every $10 rise in oil adds about five cents per pound to polyethylene, according to Morales.

From Barron's ● May 12, 2026

“Over the years military planners have arrived at a rule of thumb which dictates that functional fighting units cannot be substantially larger than 200 men,” Dunbar writes.

From "The Tipping Point" by Malcolm Gladwell

Related Words

• criterion