You can access the IRS website for that information or request a publication 15-T and they will send it directly to your home.
Where To Find Payroll Deduction Percentages Fica Sdi Medical Etc?
The percentages for social security is 6.2%, medicare is 1.45% and federal is based on the federal tables. You can get more information if you go IRS.gov and download Publication 15(Circular E). It has everything you need to know about the taxes and federal tables.