A woman in a green sweater at a kitchen table in the evening, tapping figures into a desktop calculator beside an open laptop, papers and a mug of tea in front of her, a brass desk lamp lit.
Most people do this once, in a panic, the week a payment is due. Worked out once and set aside as the money arrives, the date stops being an event.

How the estimate works

It follows the same steps as the return, in the same order:

  1. Self-employment tax. 15.3% on 92.35% of your profit: 12.4% for Social Security, up to the 2026 wage base of $184,500 (shared with any W-2 wages), and 2.9% for Medicare, with no cap. Above $200,000 ($250,000 joint) the extra 0.9% Medicare tax applies too.
  2. Half of that comes off your income. The employer-equivalent half of self-employment tax is deductible before income tax.
  3. The 2026 standard deduction ($16,100 single, $32,200 joint, $24,150 head of household) and the 20% qualified business income deduction come off next.
  4. Income tax on the 2026 brackets, stacked on top of any wages, so the business is taxed at the rates it actually reaches rather than one flat guess.
  5. State tax as a flat rate on the business income, which is close enough to plan with in most states.

On the example above, $85,000 of profit for a single filer, that comes to $17,800 of federal tax: $4,450 a quarter. The number most people guess first, 25% or 30% of everything, is close for some and badly off for others, which is the reason to work it through.

The safe harbor, and why it matters on uneven income

You don’t have to predict this year exactly. There is no underpayment penalty if what you pay through the year (estimates plus any withholding) reaches the smaller of 90% of this year’s tax or 100% of last year’s, rising to 110% of last year’s if your adjusted gross income was over $150,000.

Last year’s figure is a number you already know, so in a year that might go well, paying it in four parts takes the forecasting out of it. Open “Use last year’s tax” above and the calculator uses whichever safe harbor is smaller.

What it leaves out

Itemized deductions, tax credits (the child tax credit is the common one), capital gains, and income other than self-employment and wages. Above $201,750 of taxable income ($403,500 joint) it assumes the smallest qualified business income deduction the rules allow, so for most businesses it errs toward setting aside slightly too much rather than too little.

Questions, answered

How do I calculate my quarterly estimated tax payments?

Estimate the year’s self-employment profit, work out the self-employment tax on it (15.3% of 92.35% of the profit), then the income tax on the profit after half that self-employment tax, the standard deduction and the 20% qualified business income deduction. Divide the year’s total by four. If you already know last year’s total tax, paying 100% of it in four parts (110% if your adjusted gross income was over $150,000) avoids the penalty however this year turns out.

When are the 2026 quarterly tax payments due?

April 15, 2026; June 15, 2026; September 15, 2026; and January 15, 2027. The periods they cover are uneven: the June payment covers only April and May, and the January payment covers September through December.

What if I missed earlier quarterly payments this year?

Pay the shortfall with the next payment rather than waiting for April. The underpayment charge is interest on the amount that was late, for the time it was late, so catching up stops it growing. This calculator spreads what is still due across the payments left in the year.

Do I need to make state estimated tax payments too?

Most states with an income tax have their own estimated payments, usually on similar dates, paid to the state rather than the IRS. Enter your state’s rate and the calculator shows a separate quarterly state figure. Check your state’s own rules for its dates and threshold.

Does W-2 withholding count toward estimated tax?

Yes. Withholding from a job counts as paid evenly through the year, whenever it was actually taken. If you also have a paycheck, raising its withholding is a legitimate way to cover the tax on your self-employment income instead of making separate quarterly payments.

Sources

  1. Rev. Proc. 2025-32 (PDF) — IRS. The 2026 brackets, standard deduction and qualified business income thresholds.
  2. Contribution and benefit base — Social Security Administration. The $184,500 wage base for 2026.
  3. Form 1040-ES, Estimated Tax for Individuals — IRS. The worksheet this follows, and the 2026 due dates.
  4. Publication 505, Tax Withholding and Estimated Tax — IRS. The safe-harbor rules, including the 110% figure.
  5. Self-employment tax (Social Security and Medicare taxes) — IRS. The 15.3% rate and the 92.35% rule.