The exact words
“Many profest Christians are like to foolish builders, who build by guess, and by rule of thumb (as we use to speak), and not by Square and Rule.”James Durham, sermons published 1685, as quoted in histories of the phrase
✓ VerifiedFound in a primary source: the original book, speech transcript, letter or recording.
What people get wrong
Common reading
The phrase comes from an English law allowing a man to beat his wife with a stick no wider than his thumb.
The phrase comes from an English law allowing a man to beat his wife with a stick no wider than his thumb.
Closer to the original
No such law ever existed, and the phrase is older than the story. It comes from using the thumb as a handy measuring tool, roughly an inch wide, in everyday trades.
No such law ever existed, and the phrase is older than the story. It comes from using the thumb as a handy measuring tool, roughly an inch wide, in everyday trades.
Timeline
- 1685The Scottish preacher James Durham contrasts building “by rule of thumb” with building by square and ruler. His “as we use to speak” shows it was already a common saying.
- 1692Sir William Hope's The Compleat Fencing Master says a poor fencer works “by rule of Thumb, and not by Art.”
- 1782A rumor spreads that the judge Sir Francis Buller said a man could beat his wife with a stick no thicker than his thumb. There is no record he said it, but cartoonists mock him as “Judge Thumb.”
- 1970s–1980sWriters start claiming that “rule of thumb” comes from an old law about wife-beating, and a 1982 U.S. government report repeats the claim.
- 1990sResearchers show that no such law existed and that the phrase was never connected to it.
Use it in a speech
Few phrases have been more unfairly accused than “rule of thumb,” which meant a practical estimate a century before anyone linked it to a law that never existed.
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Questions people ask
What does rule of thumb mean?
A rough guide based on practice and experience, not precise calculation.
Does rule of thumb come from wife-beating?
No. There was never a law allowing a man to beat his wife with a stick no thicker than his thumb, and the phrase appears in print by 1685 with no such meaning.
Where does it really come from?
Probably from tradespeople using their thumbs to measure things roughly, for example as an inch.
Is it offensive to say rule of thumb?
Some organizations avoided it because of the myth, but historians agree the phrase has nothing to do with violence.
Cite this quote
This is a traditional proverb, so it counts as common knowledge and most style guides don't ask you to cite it. If you want to say where it comes from, give the earliest known use: English expression; first found in a sermon collection by James Durham (1685).