rule of thumb
"rule-of-thumb" is a 11-letter English headword indexed on PlainSpell.
The verdict
“rule of thumb” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.
- Unranked
- below top-frequency English
- 13
- letters
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A general guideline, rather than a strict rule; an approximate measure or means of reckoning based on experience or common knowledge.
| Property | Value |
|---|---|
| Headword | rule of thumb |
| Language | English |
| Part of speech | Noun |
| Letters | 13 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “rule of thumb” sits in English frequency
Rare enough to double-check
rule of thumb is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. 2 senses are on record.
Zero misspellings are on record for rule of thumb in our index, since its letter sequence doesn't invite the usual edit-distance slips. We don't track a confusable pairing for this entry, which typically means the spelling is too distinctive to be mistaken for another word.
Etymologically, the entry records: Attested since 1658. Of uncertain origin, but probably based on the use of the thumb as reference for various measurements. For instance, one theory notes that the inch originated as the distance between the base of the thumbnail and the first joint, anothe… The correct English form is rule of thumb, spelled R-U-L-E- -O-F- -T-H-U-M-B.
Definition
- 1A general guideline, rather than a strict rule; an approximate measure or means of reckoning based on experience or common knowledge.
- 2Approximated, guesstimated.
Etymology
Attested since 1658. Of uncertain origin, but probably based on the use of the thumb as reference for various measurements. For instance, one theory notes that the inch originated as the distance between the base of the thumbnail and the first joint, another notes the practice of approximating the general direction of the wind by wetting the thumb then raising it in the air. A third theory notes that English royal banquet plate setters used the distance of their thumbs to equally space each plate from the table edge. The erroneous claim that the term referred to the maximum thickness of a stick with which it was permissible for a man to beat his wife has appeared in The Washington Post and Time; it may originate from Del Martin's 1976 book Battered Wives.
This word in other languages
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.
Frequently Asked Questions
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Using “rule of thumb”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is R-U-L-E- -O-F- -T-H-U-M-B - every other letter order is a misspelling in standard orthography.
- Browse more English words and confusable pairs in the same reference. English words
Data Source
Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.