Meaning of the word "off the top of your head" in English

What does "off the top of your head" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

off the top of your head

US /ɔf ðə tɑp əv jʊər hɛd/
UK /ɒf ðə tɒp əv jɔː hɛd/
"off the top of your head" picture

Idiom

from memory, without careful thought or checking facts

Example:
I can't tell you the exact number off the top of my head, but it's around fifty.
Can you name three capital cities off the top of your head?