W-4 Allowances, Federal Income Tax Withholding

 Is there a table available where I can calculate how much will actually be withheld from my paycheck when I make a change on my W-4? 

Yes, there is. It is the same table, or tables, that employers use to determine how much to withhold based on the Form W-4 (PDF), Employee's Withholding Allowance Certificate. In Publication 15 (PDF), Circular E, Employer's Tax Guide, there are two sets of income tax withholding tables: the Percentage Method Tables and the Wage Bracket Method Tables. The wage bracket method is probably the most commonly used method. There are separate tables under each method based on marital status and payroll period. These tables are not to be used to decide how many allowances should be claimed.

Do I put the same number of exemptions on my tax return as I put on my W-4 form? 

What you put on your Form W-4 (PDF), Employee's Withholding Allowance Certificate, are withholding allowances, not exemptions. An exemption is allowed on your tax return for yourself, your spouse (if married filing jointly), and qualifying dependents (if you are an U.S. citizen or resident alien). Each exemption merits a withholding allowance on the Form W-4 Personal Allowance Worksheet.

However, there are two more worksheets that may affect the final number of allowances, and under some circumstances, you get more allowances than you have exemptions. Some things that will be on your tax return, such as itemized deductions, tax credits, and losses add allowances to the total number of allowances. Some circumstances reduce the number of allowances, such as non-wage income, having two jobs, or having two earners in the family. For a more detailed discussion of withholding allowances, refer to Publication 505 (PDF), Tax Withholding and Estimated Tax.