How many exemptions you should claim also depends on your annual income, the income you have earned so far, and the amount of withholding you have had so far.
The IRS has a great calculator tool to help you figure out how many exemptions you should claim on your Form W4. Once you click the link and review the instructions, click the blue "Withholding Calculator" box: https://www.irs.gov/individuals/irs-withholding-calculator.
