Off the top of your head
Definition 1 of 1
Pro Tip 1/3Not Prepared
Use when you haven't had time to plan or rehearse your answer. 
I haven't reviewed the report, but off the top of my head, the sales numbers are up.
Pro Tip 2/3Informal Context
Better suited for casual conversation, not for formal or serious situations. 
Off the top of my head, I'd say let's meet at the usual café.
Pro Tip 3/3Honesty Implication
Conveys a sense of honesty since the response isn't carefully crafted. 
Just off the top of my head, I think this design looks more appealing.