The IRS has a great Tax Withholding Estimator that is simple and easy to use; just fill out the questions and the program will let you know your anticipated liability or refund based upon your current level of withholding and the estimated tax payments you have made so far. It covers situations like multiple jobs, employment and self-employment, investment income, etc.
You can find the tax withholding estimator here: https://apps.irs.gov/app/tax-withholding-estimator
Here is a link that explains a little bit more about the tax withholding estimator tool: https://www.irs.gov/individuals/tax-withholding-estimator
Please be sure to have your most recent paystubs, plus any other necessary records to determine your total expected income for the year. It is also helpful to have a copy of the past year's tax return handy, so you can refer to it to determine which credits/deductions you took in the past.
