off the top of your head

US /ɔf ðə tɑp əv jʊər hɛd/
UK /ɔf ðə tɑp əv jʊər hɛd/
"off the top of your head" picture
1.

凭记忆, 不假思索地

from memory, without careful thought or checking facts

:
I can't tell you the exact number off the top of my head, but it's around fifty.
我不能凭记忆告诉你确切的数字,但大约是五十。
Can you name three capital cities off the top of your head?
你能不假思索地说出三个首都吗?