In order to know if you're eligible for a Roth IRA, income limits are based on your Modified Adjusted Gross Income. You probably don't know what yours is off the top of your head, so here are some general guidelines to help you estimate yours.
To start with, you need to know your income. This includes not only your wages, but any interest, dividends, rental income, capital gains, and business income.
Then, adjustments are made by calculating standard deductions. These deductions include the full list of deductions allowed on the first page of an IRS 1040 form. Standard adjustments include things like retirement contributions (not to Roth accounts), student loan interest, tuition, and self-employed health insurance payments.
Modifications include adding back certain deductions. Yes, we're aware at this point you're probably rolling your eyes. We're with you. This is silly. Some of the modifications include adding back deductions for student loan interest, IRA contributions, and rental losses.
Once you've taken out and then put back in some of the deductions, you will have your Modified Adjusted Gross Income. This number will help you understand your eligibility and contribution limits for a Roth IRA.
The best way to do this for your own income is on your tax form or with an accountant.