How much money would I have to pay in Taxes on a withdrawal from my 401k?

Last year I made about $18,500 in income. I currently have about $12,000 dollars in my 401k. I know its a bad idea and inadvisable to withdrawal from your 401k, but to soothe my curiosity, how much would I have to pay in taxes if I withdrew all $12,000? I know there is a big penalty fee for withdrawing early, and that the taxes they take away are massive, Im just very curious. If it helps, I live in Texas, so we don't state income tax (not sure if that applies for a 401k withdrawal though)