How much tax will there be on a $5000 401 k withdrawal

Depends on your tax bracket. Plus a $500 penalty.

The plan administartor should withhold federal tax of 20% of the withdrawal amount, or $1000 in this case. This is to help cover the actual amount of tax that is due, which as SG says depends on your particular tax bracket, so can't really be determined until you file your taxes next year. The administrator will not withhold any MD state tax, nor will they withhold anything for an early withdrawal penalty. Consequently you should be prepared to pay the MD income tax and 10% early withdrawal penalty (if required) when you figure your taxes next April.