Social Security tax is actually two taxes, one for retirement, the other for Medicare. Together, they add up to 7.65% of salary up to $128,400. After that amount, you only pay 1.45% for the Medicare portion of the tax.If by u201cfederal,u201d you mean income tax, the calculation is a bit more complex. The federal income tax is a progressive tax, meaning that as your income rises, the percent you must pay in taxes rises, too. The IRS provides employers with tax tables to enable them to withhold the correct amount from your wages, but this only holds true if your income is steady throughout the entire year, your only source of income is the wages from that one job, and if the information you provided on your W-4 form was correct. The tables are for weekly, bi-weekly, semi-monthly, and monthly pay, and, assuming that you get the exact same amount in every paycheck on that schedule for the entire year, you donu2019t itemize deductions, this job is your only source of income, and assuming that the number of dependents and marital status from your W-4 was the same throughout the year, at the end of the year, the correct amount of federal income tax will have been withheld. You will owe nothing, and they will owe you no refund. However, the vast majority of wage-earners donu2019t fit into this category. Their income is not always that regular, or they have more than one job during the year, or they have some other source of income, such as interest, dividends, or business income, or they itemize deductions on their tax return, or their marital status or number of dependents may have changed. Itu2019s a fairly complex subject. You certainly donu2019t have to have specialized training to understand it, but you do have to study it and make your way through some fairly dense IRS publications.