Side Hustle Tax Calculator
Estimate the self-employment and income tax on side income earned alongside a W-2 job.
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Side income from freelancing or a small venture is taxed differently from a paycheck: you owe self-employment tax on top of income tax, and that income tax stacks on top of your day job's wages. This calculator estimates all of it. Enter your side hustle's gross earnings and business expenses, your W-2 salary, your filing status and state, and it returns the self-employment tax, the extra federal income tax your side work triggers, any state tax, and a suggested quarterly payment. It runs entirely in your browser, so your earnings and expenses stay on your device.
How the estimate is built
First, your net profit is gross side income minus expenses (a simple total or an itemized list). Self-employment tax then applies to 92.35% of that profit — 12.4% for Social Security (coordinated with your W-2 wages up to a combined $176,100 ceiling) plus 2.9% for Medicare. Half of the self-employment tax is deducted before income tax is figured.
Added federal tax = tax(W-2 + net profit − ½ SE tax) − tax(W-2 alone)
Because your side profit sits on top of your salary, the tool taxes your combined income and subtracts the tax you would owe on the W-2 alone, isolating the extra federal tax the side hustle causes. It uses the standard deduction ($15,000 single, $30,000 married, $22,500 head of household) and the federal brackets from 10% to 37%. State tax, where it applies, is a flat rate on net profit.
A worked example
Say you earn $15,000 on the side with $2,000 of expenses, on top of a $50,000 salary, filing single in a no-income-tax state. Net profit is $13,000. Self-employment tax comes to about $1,837. Stacking the $13,000 (less half the SE tax) on your salary adds roughly $1,450 of federal income tax at the 12% band. With no state tax, the total side hustle tax is about $3,287 — an effective rate near 25% of net profit — which the tool splits into quarterly estimated payments of about $822. The savings box also shows how much your write-offs trimmed the bill, valued at your combined self-employment, marginal income, and state rates.
What it assumes and leaves out
This is a planning estimate, not tax advice. It assumes the standard deduction and treats your side work as a sole proprietorship subject to self-employment tax. The state figures are flat-rate approximations — real state systems are often progressive with their own deductions — so the "8% average" for California or "6% average" for New York is a rough stand-in, and you can override it with a custom rate. The federal brackets and the standard deduction shown reflect recent tax-year figures, which the IRS adjusts annually. It does not model the qualified business income (QBI) deduction, retirement contributions, credits, or business structures like an S-corp. Confirm current figures for your filing year and check with a tax professional before relying on the numbers.
Frequently Asked Questions
Does this calculator store my income or expenses?
No. Everything is calculated in your browser. Your side income, expenses, salary and other entries are never uploaded or saved, and reloading the page clears them.
Why do I owe self-employment tax on top of income tax?
On a W-2 paycheck your employer pays half of Social Security and Medicare. When you work for yourself you cover both halves — 15.3% on 92.35% of net profit — which is the self-employment tax. Income tax is separate and stacks on top of your other income.
What is the quarterly payment for?
Side income usually has no withholding, so the IRS expects estimated tax payments through the year. The tool divides the total estimated side hustle tax by four as a starting point for those quarterly payments.
Is this tax or financial advice?
No. It is general information for planning only. State rules are approximated, tax figures change yearly, and your real liability depends on your full situation, so consult a qualified tax professional.