Here's a REALLY handy payroll calculator that calculates both state and Federal taxes.   Make sure you're getting paid correctly....believe it or not at my last job in Florida I caught a major error in the payroll department.   They were deducting TWICE the amount of tax out of my check then they should have.  Not only for my check, but 4 other employees.   Nobody even noticed!!!!!!!!!!!!!!!!!!!!!!!!!    I was the only one going "GEE....that's an AWFUL LOT OF MONEY TO BE TAKING OUT OF MY CHECK...."   Forget the check being wrong........I think it was actually more shocking and appalling that NOBODY ELSE even noticed that their paychecks were way off and unusually low.  I mean....is the population that asleep?!?     Oh wait...nevermind.....       Anyway, I went online to hunt down some way to figure out what the tax deduction should be, found a good link and discovered that sure enough, they were deducting my taxes as if I was being paid weekly...when I was actually being paid bi-weekly.   BIG DIFFERENCE.     !    So needless to say, you never know, mistakes do happen, and I've seen it. Luckily I discovered it and immediately was refunded all the extra money they had taken out. 

http://www.paycheckcity.com/conpw/netpayCalcResult.asp

It's pretty straight forward, you just select "Per Pay Period" at the top, type in what your gross check amount is, and whether you're being paid weekly, bi-weekly, semi monthly, monthly, etc.  then, how many dependents you're claiming for your Federal tax.   If State tax applies, then put the # of dependents you're claiming for State as well.   Then press Calculate, and ouila!    Up pops the net amount for your check.  Compare it to your check and make sure everything matches up.