This is a very vague question but I will still try to give my best.Lets assume your income for year 2018(as an intern) is $40000. After taking the standard deductions of $4,236 your taxable income becomes ~$35700. You would have to look up in the tax table to figure out your taxes 2023 California Tax Rates and Exemptionstaxes for $35700 is roughly $2300. Note this is a guess work.This is a very basic example. Based on your financial situation this calculation would be different.Since you are one f1 visa you might be considered non resident alien. This software gives you an eof taxes after entering your w-2 information for FREE. Taxes for non-resident aliens