you know as well as I do

you know as well as I do

We both know equally well (that something is true). Used rhetorically to remind or convince someone about something. I know we need money, but you know as well as I do that we could go to prison for getting involved in something like this. Now Tim, you know as well as I do that your parents don't allow you to have sugary snacks, so you can't have any here.
See also: know, well
Farlex Dictionary of Idioms.

ˌyou know as well as ˈI do

used when you are trying to convince somebody that something is true: You know as well as I do that if she finds out, she’ll stop us going.
See also: know, well
Farlex Partner Idioms Dictionary
See also:
  • closed book, a
  • a closed book
  • I know
  • know (someone or something) inside out
  • know inside out
  • know somebody/something inside out
  • know someone or something inside out
  • know something/someone inside out
  • as we know it
  • by any chance