Quarterly Estimated Tax

Combining Self-Employment Tax and Income Tax Into One Quarterly Payment

Quarterly estimated tax is the self-employed equivalent of paycheck withholding — four payments a year, each covering roughly a quarter of your total expected federal tax bill. Enter your expected net self-employment earnings and filing status, and this calculator combines your self-employment tax (Social Security and Medicare) with your federal income tax into one total, then divides it into four equal quarterly payments.

This is the one number the Self-Employment Tax Calculator and Income Tax Calculator calculators don’t give you on their own — each estimates one piece of the full year’s tax bill; this one combines both and does the quarterly division.

The Formula

1. Self-employment tax — 92.35% of net earnings, taxed at 12.4% Social Security (capped at the annual wage base) plus 2.9% Medicare (uncapped), the same formula the Self-Employment Tax Calculator uses.
2. Federal income tax — computed on taxable income (total income minus half the self-employment tax minus the standard or itemized deduction), using the current-year federal brackets for your filing status.
3. Total estimated tax = self-employment tax + federal income tax.
4. Quarterly payment = total estimated tax ÷ 4.

Worked Example

$80,000 in expected net self-employment earnings, filing single, no other income, no itemized deductions:

1. Self-employment tax: $80,000 × 92.35% = $73,880 subject to SE tax → $73,880 × 12.4% + $73,880 × 2.9% = $11,303.64.
2. Taxable income: $80,000 − $5,651.82 (half the SE tax) − $16,100 (2026 single standard deduction) = $58,248.18.
3. Federal income tax on that taxable income: $7,728.60.
4. Total estimated tax: $11,303.64 + $7,728.60 = $19,032.24.
5. Quarterly payment: $19,032.24 ÷ 4 = $4,758.06, due mid-April, mid-June, mid-September, and mid-January.

Key Factors to Consider

• The four quarterly due dates aren’t actually evenly spaced across the calendar year. The IRS’s own quarters run mid-April to mid-June, mid-June to mid-September, mid-September to mid-January, and mid-January to mid-April — unevenly sized windows rather than clean 3-month blocks, which can catch a first-time filer off guard if they assume a simple quarterly calendar.
• Underpayment penalties can apply even to someone who eventually pays their full tax bill by the annual filing deadline. The IRS generally expects tax to be paid throughout the year as income is earned, not all at once at filing time — consistently underpaying each quarter can trigger a penalty even if the total amount owed is fully paid when the return is filed.
• Income that fluctuates significantly through the year makes a flat quarterly estimate less accurate than reality. Someone with seasonal or highly variable self-employment income may benefit from the IRS’s “annualized income installment method,” which adjusts each quarter’s required payment based on income actually earned so far that year, rather than a flat one- quarter-of-the-annual-estimate approach.
• State estimated tax payments are typically a separate obligation from federal ones. Most states with an income tax require their own quarterly estimated payments on a similar (though not always identical) schedule — this calculator estimates federal tax only, so a state’s own quarterly requirement needs to be checked and paid separately.

Common Mistakes

• Waiting until the deadline to figure out what to pay. Estimating early in the year (and adjusting each quarter as actual income becomes clearer) avoids a scramble — and a possible penalty — at the final deadline.
• Forgetting the self-employment tax half. It’s easy to estimate income tax alone and forget that self-employment tax (often the larger of the two for a moderate income) is due on the same schedule.
• Ignoring the safe harbor option. If this year’s income is hard to predict, paying based on last year’s actual tax liability (the “safe harbor” amount) is often simpler and just as protective against a penalty as trying to nail this year’s number exactly.

Useful to Know

• Want to isolate just the Social Security/Medicare portion of this bill? Self-Employment Tax Calculator calculates self-employment tax on its own.
• Want to see the full-year federal income tax picture, including other income or deductions? Income Tax Calculator handles the general income tax calculation.
• Setting your own freelance rates to make sure quarterly taxes are covered? Freelance Hourly Rate Calculator helps price your work with taxes factored in.