Quarterly estimated tax calculator (2026)

How the payment is worked out

The calculator follows the 2026 Form 1040-ES worksheet. Self-employment tax comes first: profit times 92.35%, then 12.4% for Social Security up to the $184,500 wage base (your own W-2 wages use part of it) and 2.9% for Medicare. Half of that tax is subtracted to reach adjusted gross income, then the 2026 standard deduction ($16,100 single, $32,200 joint) and the qualified business income deduction. Income tax comes from the 2026 rate schedules, and the two taxes are added.

Then the safe harbor. You avoid the underpayment penalty if withholding plus estimated payments reach the smaller of 90% of your 2026 tax or 100% of the tax on your 2025 return, rising to 110% when your 2025 adjusted gross income was over $150,000. Withholding is subtracted, and the rest is split into four equal payments. If that leaves nothing, or if your 2026 tax minus withholding is under $1,000, the worksheet says you are not required to pay estimated tax.

When last year's tax is the smaller number, the four payments only buy you penalty protection. The rest of the 2026 bill is still due with the return, which is what the last box shows. Paying 100% of a small prior-year tax and parking the difference is the plan for a first good year, explained in quarterly estimated taxes for creators.

The four dates assume you start in April. If some have already passed, those payments are late, not cancelled: the IRS figures the penalty from the amount underpaid, how long it stayed unpaid and its quarterly interest rate, so paying now still shortens the clock.

The QBI deduction, and what is left out

Below the 2026 threshold ($201,750 of taxable income before the deduction, or $403,500 joint), the qualified business income deduction is the smaller of 20% of business income or 20% of taxable income. Business income here is profit minus half of self-employment tax, so the calculator assumes you pay no self-employed health insurance and make no retirement contributions; both would lower it. From 2026 the deduction is at least $400 when you have $1,000 or more of income from a business you materially participate in, which the calculator assumes. Above the threshold the wage and property limits kick in, so it shows no deduction and the estimate runs high.

Left out: state and local tax, every credit (including the child tax credit), the alternative minimum tax, the 0.9% Additional Medicare Tax, the 3.8% net investment income tax, capital gains and qualified dividends, itemized deductions, the Schedule 1-A deductions, head of household and married filing separately status, and a spouse with self-employment income of their own. If your income is lumpy, the annualized method on Form 2210 Schedule AI can lower the early payments; this uses the equal four-way split.