Only income earned from working is considered for the earned income credit. Other types of income, like Social Security, rental income, investment income etc. do not increase the amount of income used to calculate your EIC. They do, however, factor in your AGI which affects the amount of EIC you can receive.
The IRS offers a tool to help you estimate your EIC:
The amount of EIC you are receiving can be seen on your Form 1040 on line 17a