How hard is it to get into a top 5 program without a t20 undergraduate

[kanemath]

I go to a decent state school and im wondering how hard would it be for me to go to a top 5 program without a t20 undergrad

 

[Andy Nguyen]

It's all relative to the strength of the applicant pools applying to those programs. Look at the QuantNet ranking and go through each program's acceptance rate to see where you need to be.
Look at the Tracker and see profiles of those making the cut.
A well prepared applicant will do well. Take all the prep courses you need to get in a top shape so you can do well in their admission interviews.