To qualify things, you should always consult a qualified certified public accountant (CPA) to get the most accurate answer to your tax questions. That said this may be more info than you really want. To say the least, our tax system is not a flat tax system, so it isn't that straight forward.
In general, you would do the following:
Business income
less: business expenses
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Net self employment income (loss)
add: other income (interest, dividends, capital gains, etc)
less: above the line deductions (IRA contributions, 50% of self employment tax)
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Adjusted gross income
less: larger of itemized deductions (mortgage interest, state, local and property taxes, charitable contributions, medical expenses in excess of the limit, and certain miscellaneous deductions), or the standard deduction for your filing status (single, married filing jointly, etc.)
less: Exemption for dependents
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Taxable income
Calculate your tax using graduated tax rates (of course you need to determine if you are subject to the Alternative Minimum Tax (AMT) and use the larger of the two amounts)
Add: self employment tax (approx. 15.3% of net self employment income)
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Tax liability
less: payments/withholding already made
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Tax due or refund
I apologize if this response is too confusing or not even allowed on TUG. I would recommend you hire a CPA to help you or buy a product like TurboTax, which will walk you through the process.
I hope this helps.