@joshjessup - use the IRS withholding calculator.
However, if there are no withholdings, you can't get more money back in your paycheck. i.e. there can not be negative federal withholdings.
it is possible that based on your income, filing status and number of children, there is no required federal withholding.
the Estimator will show you exactly how to complete your W-4.
https://www.irs.gov/individuals/tax-withholding-estimator
