off the top of one's head

/ˈɒf ðə tˈɒp ɒv wˈɒnz hˈɛd/

/ˈɔf ðə tˈɑːp ʌv wˈʌnz hˈɛd/

off the top of one's head

from one's memory, without spending time to carefully consider or think

Examples

1. It was the best I could think of off the top of my head.

2. Just off the top of my head, I’d say there were about 50.

3. John can list the capital cities of all 50 states off the top of his head.

4. I need to stop relying on things because I can't even tell you off the top of my head all of what I have.