The dollar amount of your paycheck depends on your wages or salary, minus your payroll adjustments. These include your income tax withholdings, contributions to work-sponsored retirement plans such as a 401(k), and other deductions such as health insurance premiums. Here's how to estimate the effect of a change in your payroll adjustments on your take-home pay.
Take-home pay calculator
Here's a quick, easy-to-use calculator that can help you determine the effect of changing your payroll adjustments on your take-home pay. After the calculator, I'll discuss the different inputs and what they might mean to your paycheck.
A user's guide to the calculator
First of all, if you're not sure what your gross earnings per pay period are, there are some easy ways to determine this amount. If you have a pay stub handy, your gross pay should be readily available. Or, if you're paid an annual salary, simply divide it by the number of times you get paid each year. For hourly employees, multiply your hourly wage by the number of hours you work per pay period.
Filing status is important, as it affects your tax withholdings. Without getting too deep into the mathematics, the general rule is that if you select the single filing status (or select an option that says "married, but withhold at higher single rate"), more will be withheld from your paycheck for income taxes.
The number of allowances you claim (also known as your "exemptions") are intended to reflect the fact that workers with more dependents get additional tax breaks. It's not a one-to-one relationship and you don't have to claim all of the exemptions to which you're entitled when filling out your payroll paperwork. However, you can determine the maximum number of allowances you should claim with this (Link opens PDF) IRS worksheet.
A word of caution when it comes to exemptions/allowances: Your goal should be to claim the proper number of allowances that match up to your actual tax liability. Claiming too many allowances with your payroll department can result in a big tax bill at the end of the year, and claiming too few can result in a big tax refund, which may sound good, but you're essentially giving the IRS an interest-free loan.
Pre-tax deductions refer to items withheld from your paycheck that are not subject to tax. Health and dental insurance are common examples. On the other hand, post-tax deductions refer to items deducted from your paycheck that don't qualify for any special tax treatment. Union dues are a common example (although they may be deductible on your tax return).
Finally, retirement contributions you make to an employer-sponsored retirement plan such as a 401(k), 403(b), or 457, are typically made on a pre-tax basis and therefore are excluded from your taxable income. So, if you increase your retirement contributions, your take-home pay will be lower, but your tax withholdings will also go down.
One thing that's missing
In the interest of being complete, it's important to point out that this take-home pay calculator only considers federal withholdings. It doesn't compute the effect of your payroll adjustments on your state or local tax withholdings. If you live in a state with no income tax, the calculator should be accurate as-is. However, if your state has an income tax, the change in your take-home pay may be somewhat different than the calculator indicates.