Estimate quarterly tax liability based on income, deductions, and self-employment tax rates.

About the Quarterly Tax Estimator

The U.S. tax system is pay-as-you-go, and when no employer withholds tax from your income the responsibility to prepay falls on you in four installments. Underpay and the IRS charges an estimated-tax penalty that behaves like interest on the shortfall. This estimator projects your full-year liability from a few high-level inputs and divides it into equal quarterly payments so you can set money aside before each deadline.

It is built for the freelancer, consultant, or small-business owner who knows their rough annual income and wants a defensible number to send in each quarter, rather than a precise return. You supply gross income, deductions, credits, and an average income-tax rate; the tool handles self-employment tax and produces a payment schedule.

Before you enter your numbers

Decide what the annual income input represents before entering it. This legacy flat-rate model applies self-employment tax to that entire input, while its deduction field reduces only the separate income-tax estimate.
For an actual return, business expenses can also change SE profit. Use the official worksheet rather than assuming this model reproduces Schedule C and Schedule SE.

Assumptions and limits

The formula is annual income × 92.35% × 15.3%, plus max(0, income − deductions) × your flat income-tax percentage, minus credits, floored at zero, then divided by four.
It does not cap Social Security, use progressive federal brackets, collect other wages or withholding, or calculate safe harbors. It is an illustrative budgeting model—not a current-year tax payment instruction.

Check your result

With $120,000 income, $25,000 deductions, a 22% flat income-tax assumption, and $1,000 credits, the model shows $16,955.46 SE tax and $20,900 income tax. After credits: $36,855.46 annually, or $9,213.87 per quarter. This reproduces the model, not a complete tax return.

How the Quarterly Tax Estimator works

Taxable income is gross income minus deductions, floored at zero. Self-employment tax is calculated as gross income × 0.9235 × 15.3% — the 0.9235 factor reflects the deductible-half adjustment built into Schedule SE, and 15.3% combines the 12.4% Social Security and 2.9% Medicare rates. Income tax applies your entered average rate to taxable income.

Total estimated tax is self-employment tax plus income tax, less any credits, floored at zero. That annual figure is divided by four to produce each quarterly payment. Because the tool uses a flat average rate rather than graduated brackets, treat it as a planning estimate — for a bracket-by-bracket calculation use the dedicated Quarterly Estimated Tax tool.

Worked example

With the defaults — $120,000 gross income, $25,000 deductions, $1,000 credits, and a 22% average rate — taxable income is $95,000. Self-employment tax is 120,000 × 0.9235 × 0.153 = about $16,956. Income tax is 95,000 × 22% = $20,900.

Adding those gives $37,856, and subtracting the $1,000 credit leaves a total estimated liability of $36,856. Divided by four, each quarterly payment is roughly $9,214, due April 15, June 15, September 15, and January 15 of the following year.

Tips & common mistakes

Use the safe harbor to avoid penalties: pay at least 90% of this year's tax or 100% of last year's (110% if your prior-year AGI topped $150,000). Hitting either number stops the underpayment penalty even if you owe more in April.
The 'deductions' field is your business write-offs and above-the-line items — not a second copy of the standard deduction if you already baked it into your average rate. Pick one approach and stay consistent.
Set aside the quarterly amount in a separate account the moment income arrives. Treating tax money as spendable cash is the most common reason freelancers fall behind.
Recompute mid-year if income swings. The equal-installment split assumes steady earnings; a big Q3 project may require topping up your September payment.

Quarterly Tax Estimator: frequently asked questions

Where does the 0.9235 factor in the SE tax come from?

Employees split Social Security and Medicare with their employer, so the self-employed get a parallel break: you only pay SE tax on 92.35% of net earnings (that is, 100% minus half of the 15.3% rate). The tool applies 0.9235 before the 15.3% so your base mirrors what Schedule SE produces.

What if my income is uneven across the year?

This estimator splits the annual liability into four equal payments, which is fine for steady income. If you earn most of your money in one quarter, the IRS lets you use the annualized income installment method (Form 2210, Schedule AI) to match payments to when income is actually received and reduce penalties.

Are the quarterly periods actually three months each?

Not evenly. Despite the name, the periods cover January–March (due April 15), April–May (due June 15), June–August (due September 15), and September–December (due the following January 15). The uneven windows trip up many first-time filers, so mark the real dates rather than assuming clean quarters.

What average income-tax rate should I enter?

Use your effective rate, not your top bracket. For many self-employed filers with mid-five-figure taxable income that lands somewhere between 10% and 18%; the 22% default is conservative. If unsure, look at last year's total income tax divided by taxable income and start there.

Do I still make estimated payments if I also have a W-2 job?

You can, but you may not need to. Increasing withholding on your W-2 via a new W-4 is often simpler because withholding is treated as paid evenly throughout the year, which can cover a side-business shortfall without separate quarterly vouchers.

Use the result in your next decision

Quarterly Estimated Tax Estimator: See a separately labeled 2025 progressive-bracket illustration and its exclusions.

Sources and further reading

These references explain the specified topic; they are not endorsements or evidence that a professional has reviewed this tool.

IRS Form 1040-ES — Use official current-year worksheets for required estimated payments.

Quarterly Tax Estimator