To use a 1099 tax estimator calculator, fill in the calculator with all income reported in the 1099 form and any additional estimated income made from wages or salary during the tax year to arrive at the tax on the self-employment amount, says Dinkytown.net. As of 2014, there is no tax on self-employment income of less than $400.
Calculate net income or loss by filling out an Internal Revenue Service form called Schedule C or C-EZ, reports TurboTax. Find this total by subtracting any business expenses, such as travel or supplies, from the gross amount reported in the 1099. This total is then reported on Form 1040, and it is taxed in the same manner as any other income reported in the 1040.
Fill in farm or church income, if applicable, says Dinkytown.net. Then estimate the year's wages to calculate the total tax responsibility, including Federal Insurance Contributions Act taxes. If the total wages, tips and self-employment income exceed a predetermined limit, $118,500 in 2014, it affects the amount owed on some FICA taxes, such as Social Security. The taxpayer is only responsible to pay Social Security taxes on the difference between the self-employment income and the predetermine limit. For example, if an employee made $100,000 in wages and $100,000 through self-employment, the taxpayer only has to pay Social Security taxes on $18,500 of his self-employment income, per the limit.