rule of thumb
Proposed by a contributor, not yet supported by evidence.
Meaning · English
A rough and approximate guide or method
Literally: a rule based on the size of a thumb
Where it’s used:
Used
Widespread English
Examples
When drawing from memory, however, it is useful to have a handy, rule - of - thumb checking device to gauge such proportions as arm - length or head - size.
A suggested rule of thumb might be 1% of the population aged 65–74, 10% of the population aged 75–84 and 25% of the population aged over 85 would have moderate / severe dementia.
British National Corpus sentence via the MAGPIE corpus (CC BY 4.0, retrieved 2026-07-30)
Sources & notes
Listed in Wiktionary’s “English idioms” category (retrieved 2026-07-29); definition pending editorial review. Definition drafted by AI (@cf/meta/llama-3.3-70b-instruct-fp8-fast) and auto-approved by rule on 2026-07-31; pending editor spot-check.
Equivalents & related
Common questions
What does “rule of thumb” mean?
A rough and approximate guide or method Literally: a rule based on the size of a thumb
Is “rule of thumb” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.
What is the closest equivalent?
“quy tắc” (Tiếng Việt) — near equivalent.