The answer to the minimum amount of income you have to earn in order to be required to file a tax return is not a "one-size-fits-all" solution, unfortunately. That said, for 2016, a single person under age 65, unmarried, not claimed as a dependent by another taxpayer, and earning less than $10,350 in gross wage income (from W-2 wages, not self-employment), does not need to file a federal income tax return.
However, even if you do not absolutely have to file a federal tax return, if you have any amount showing in Box 2 of your W-2 as income taxes withheld, or if you think you might qualify for a federal tax credit (such as for health insurance or the Earned Income Credit), then you may wish to file anyway . . . even if you don't need to. Filing a tax return is the only way to see if you are eligible for any tax refunds or credits from the IRS. And with TurboTax, simple tax returns can be completed and filed for free. You can visit the following link to learn more:
https://turbotax.intuit.com/personal-taxes/online/free-edition.jsp
Also, if the above taxpayer situation does not accurately or fully describe you (W-2 only wage earner, single, under age 65, no self-employment income, not claimed as a dependent on parent's tax return), then you will want to see the "Do I Have To File A Tax Return?" instructions found in IRS Publication 17, which begin at the bottom of Page 4 and run through to Page 8 for a full and complete discussion. In other words, reading those pages of Publication 17, and applying the rules found there to your own unique circumstance, will absolutely tell you, with one-hundred percent accuracy, whether or not you legally must file a federal tax return this year.
Here is a courtesy link to IRS Publication 17:
https://www.irs.gov/pub/irs-pdf/p17.pdf
Thank you for asking this important question.