ENGLISH
REFERENCE

act one's age, not one's shoe size

idiom
Meaning

Synonym of act one's age (“to behave in a mature manner; to avoid being childish”).


Origin

disputed origin

In reference to a person's shoe size (in the US or UK shoe size systems) usually being much lower than their age.

Examples
SIMPLE

Please stop acting your age, not your shoe size.

CONTEXTUAL

The teenagers were throwing food in the cafeteria, so the teacher told them to act their age, not their shoe size.

COMPLEX

Despite his professional title, he continued to make immature jokes during the board meeting, prompting his colleague to suggest he finally act his age, not his shoe size.

Anchors to
Related idioms8entries
  1. 01

    abound in one's own sense

    To follow one’s own inclinations and opinions.

  2. 02

    ace up one's sleeve

    A surprise advantage of which others are not aware.

  3. 03

    act of Congress

    An authorization that is extremely difficult to obtain, especially in a timely fashion.

  4. 04

    act one's age

    To behave in a manner appropriate to one's age.

  5. 05

    act out

    To perform something specific.

  6. 06

    act the hypocrite

    To behave deceitfully or hypocritically; to dissemble.

  7. 07

    act up

    To misbehave; to cause trouble.

  8. 08

    afraid of one's own shadow

    Exceptionally timid.

© 2026 English Reference