Estimated tax payment calculator

Work out your quarterly estimated tax as a self-employed filer — self-employment tax and income tax together, sized to the safe-harbor target the IRS actually requires.

How the math works

The calculator builds your full-year federal tax from two pieces, then sizes the quarterly payment to whichever safe harbor is smaller.

First, self-employment tax. This is the 15.3% that covers both halves of Social Security and Medicare, and it is charged on 92.35% of your net profit rather than the whole figure. The 12.4% Social Security portion stops at the $168,600 wage base; the 2.9% Medicare portion never stops.

Second, income tax. Half of the self-employment tax comes off your income first, then the standard deduction, and the 2024 brackets run on what is left. The two taxes add up to your projected full-year total.

Then the part the other calculators skip. You do not have to pay your whole projected tax through the year. You avoid the penalty by paying the smaller of two targets: 90% of this year's tax, or 100% of last year's tax — 110% if last year's AGI was over $150,000. Divide that target, less anything already withheld, into four.

Worked example

Take a full-time freelancer, filing single, with net profit of $59,540 — the U.S. median individual earnings for full-time workers. No W-2 job, nothing withheld, and this is not their first year, so last year's return exists.

Self-employment tax first: $59,540 × 0.9235 is $54,985.19 of net earnings, and 15.3% of that is $8,412.73. Half of it, $4,206.37, is deductible. So adjusted gross income is $55,333.63, and after the $14,600 standard deduction the taxable figure is $40,733.63.

Income tax on that, single: 10% on the first $11,600 and 12% on the rest works out to $4,656.04. Add the two taxes and the full-year total is $13,068.77. The current-year safe harbor is 90% of that — $11,761.89, or about $2,940 a quarter.

Now the second target. Say last year, a slower year, this filer's total tax was $9,000 and their AGI was under $150,000. The prior-year safe harbor is 100% of that, $9,000 — about $2,250 a quarter. That is the smaller number, so it is the one the IRS requires. Paying it protects the filer from the penalty even though they will still owe the difference next April.

When this calculator is wrong

The result is a clean four-way split of an annual target. Real self-employment income rarely arrives that way, and the tax code has more corners than one number can hold.

• It assumes four equal payments. Estimated tax is charged per period, not once a year. If your income is lumpy — a quiet spring and a heavy fourth quarter — the flat split can leave you "underpaid" on the early quarters and owing a penalty even if you square up by December. The fix the mainstream calculators never mention is the annualized income installment method on Form 2210 Schedule AI, which lets you pay each quarter from the income you had actually earned by then. Once you use it for one quarter you must use it for all four.
• A big year-end payment does not cure an early shortfall. The penalty is interest, not a flat fine — the federal short-term rate plus 3 points, run between 7% and 8% across 2024–2025, and it accrues on each quarter's gap for the days it sat unpaid. Catching up in the fourth quarter stops the clock going forward; it does not refund the interest already owed on the first.
• It leaves out a few real taxes. There is no state estimated tax here, and most states with an income tax run their own quarterly schedule. It also omits the extra 0.9% Additional Medicare Tax on earnings above $200,000 single or $250,000 married filing jointly, and the 3.8% net investment income tax on investment income over those same lines.
• The prior-year target needs a prior year. In your first self-employed year there is no last-year tax to lean on, so the 100–110% safe harbor is unavailable and the 90%-of-this-year path is the only one. That is the year the forecast actually has to be good.

What to do with the result

If you have last year's return and this year is shaping up bigger, the simplest penalty-proof move is to pay 100% — or 110% if last year's AGI cleared $150,000 — of last year's total tax, split into four, and settle the rest when you file. You are paying a known number instead of betting on a forecast, and the extra you will owe in April sits in your own account earning interest until then rather than the government's.

Set the payments on the calendar now: April 15, June 15, September 15, and January 15 of the following year, each shifting to the next business day when it lands on a weekend. Pay through IRS Direct Pay or EFTPS rather than mailing a voucher. If your income is genuinely seasonal, read the Schedule AI instructions before the first payment, not after the last one.

Common questions

Do I actually have to pay quarterly?

You are required to pay estimated tax if you expect to owe $1,000 or more for the year after withholding and credits. Below that, you can settle the whole thing when you file. A side gig on top of a W-2 job often stays under the line if the W-2 withholding is high enough — this calculator's "tax already withheld" field is where that shows up.

What happens if I skip a payment?

The IRS charges an underpayment penalty, which is really interest on the shortfall at the federal short-term rate plus 3 points, reset each quarter and recently between 7% and 8%. It is not catastrophic on a small gap, but it is charged per quarter, so an early miss keeps accruing even after you catch up.

Can I just pay it all in the fourth quarter?

Not without a penalty, under the standard method. Because each quarter is assessed on its own, a lump payment in January does not backfill the April, June, and September installments. The exception is the annualized income installment method, which is built for exactly the case where the income itself arrived late in the year.

Should I base the payment on this year or last year?

Whichever is smaller, because meeting either one avoids the penalty. Last year's tax is a fixed number you already know; this year's is a forecast. When your income is rising, the prior-year target is usually both smaller and safer, so it is the one to pay through the year.

Does self-employment tax replace income tax?

No — it is on top. Self-employment tax is the Social Security and Medicare piece, the 15.3% a wage earner and their employer split; income tax is separate and stacks on the same profit. Estimated payments have to cover both, which is why the number surprises people in their first self-employed year.