DictionaryAI

rule of thumb

noun
Sayrool uhv THUMUS/ˌɹul əv ˈθʌm/UK/ˌɹuːl əv ˈθʌm/ROOL uhv THUM

Pluralrules of thumb

2 meanings of rule of thumb

Practice

  1. 1
    nouncountable
    A simple guide based on experience that usually works, but is not an exact rule.

    Like a quick guess that is usually close enough, not a careful measurement.

    As a rule of thumb, you should drink water before you feel thirsty.

    A good rule of thumb is to save part of every paycheck.

    Similarguideline, heuristic

    Note
  2. 2
    nounbefore a noun
    Worked out by a rough guess instead of careful measurement.

    Like measuring something with your hand instead of a ruler: close, but not exact.

    We made a rule-of-thumb guess about how long the trip would take.

    Their rule-of-thumb estimate of the cost turned out to be close.

    Similarballpark

    Note

Practice

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Origin

This phrase has been used since 1658. Its origin is not certain, but it probably comes from using the thumb to measure things.