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

A common rule of thumb for builder investors is buy the stocks when they trade at one-times book value and sell at two-times book value.

From Barron's • Apr. 12, 2026

Applying that rule of thumb to a persistent $5- to $15-a-barrel Iran-related premium—roughly a 7% to 21% oil shock at current price levels—suggests a drag of about 0.1% to 0.4% on global output.

From The Wall Street Journal • Mar. 12, 2026

When looking for a sweet spot to buy back into stocks, Nicholas Colas, co-founder of DataTrek, told MarketWatch that seeing the VIX close at 27.5 or above is as a solid rule of thumb.

From MarketWatch • Mar. 3, 2026

A rule of thumb among economists is that a 5% increase in oil prices raises year-over-year measures of inflation by about 0.1 percentage points.

From The Wall Street Journal • Mar. 3, 2026

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

From "The Big Short" by Michael Lewis

Related Words

• criterion