Hey,
I am on OPT Visa working full time. I pay Federal and state taxes.
Lets say I will pay more than 10k in the whole year, How much (what %) would I get back as refund on tax returns.
Any help would be appreciated!
Thanks.

That would depend on other things as well.
What is your gross income?
How long have you been in the US? (to determine if you need to file 1040 or 1040NR)
Are you married? Children? Where are you from?