What this calculator does
Find out how much to send the IRS each quarter in 2026, and when each payment is due. If you earn money with no tax taken out, the IRS wants tax on it during the year. That includes freelance or gig income, rent, interest and side businesses. You pay it in four installments called quarterly estimated payments. If you pay too little or too late, you can owe a penalty, even if you pay the full balance in April.
This calculator estimates your 2026 federal tax, including self-employment tax (Social Security and Medicare tax for people who work for themselves). Then it applies the safe harbor rules from Form 1040-ES. A safe harbor is a minimum that protects you from the penalty. You're covered if your withholding and estimated payments add up to the smaller of two amounts. One is 90% of your 2026 tax. The other is 100% of your 2025 tax, or 110% if your 2025 AGI was over $150,000. (AGI, adjusted gross income, is your income after a few adjustments, before deductions.) The calculator splits the amount you need into four payments and lists their due dates.
Where it's used
Why this math matters outside the classroom:
- Freelance budgeting. A freelancer who owed $9,000 last year divides by 4 and pays $2,250 on each estimated tax due date.
- Safe harbor choice. Someone expecting $12,989 of tax compares 90% of it, $11,690.10, with last year's $9,000 and pays the smaller.
- Self-employment tax. A designer with $60,000 of net profit owes 15.3% of 92.35% of it, or $8,477.73, in self-employment tax.
- Rental income. A landlord with $18,000 of net rent and no withholding schedules four payments to avoid an April surprise.
- Side-gig workers. Rideshare drivers with a day job raise W-4 withholding instead, since it counts as paid evenly through the year.
Grade level and standards: Grade 7; Common Core State Standards for Mathematics 7.RP.A.3. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose your filing status. Enter your expected 2026 self-employment net profit, wages and other taxable income.
- Add any extra deductions and credits, and the federal tax you expect to have taken out of paychecks this year.
- Enter the total tax and AGI from your 2025 return. This lets the calculator use last year's tax as a safe harbor.
- Read the payment due each quarter and the table of due dates. You'll also see the amount that would cover your whole 2026 tax.
What the inputs mean
- Self-employment net profit for 2026 (optional)
- Net profit is your business income minus the expenses you can deduct. It's the bottom line of Schedule C. Self-employment tax applies to 92.35% of it.
- Other taxable income (optional)
- Interest, dividends, rent, taxable retirement income and the like.
- Other deductions (optional)
- The calculator already uses the standard deduction. Enter anything else that lowers your taxable income here. Two common ones are deductible IRA contributions and the qualified business income deduction. That one can be up to 20% of qualified business income for many sole proprietors (one-person businesses).
- Federal tax withheld in 2026 (optional)
- Tax withheld from a job, pension or other payments counts as paid evenly through the year, no matter when it was actually taken out. That makes extra withholding an easy way to catch up late in the year.
- Total tax on your 2025 return (optional)
- Use the 'total tax' line from your 2025 Form 1040, not the balance you paid in April. If your 2025 tax was zero and you were a citizen or resident all year, you don't need to make estimated payments for 2026.
- 2025 adjusted gross income (optional)
- If your 2025 AGI was over $150,000 ($75,000 if married filing separately), last year's safe harbor goes up from 100% to 110%.
Formula and method
SE tax = 15.3% × (92.35% × net profit), Social Security part only up to $184,500 AGI = wages + other income + net profit − ½ SE tax 2026 tax = bracket tax on (AGI − standard deduction − other deductions) − credits + SE tax required = smaller of 90% × 2026 tax and 100% (or 110%) × 2025 tax each payment = (required − withholding) ÷ 4; none needed if 2026 tax − withholding < $1,000
SE tax is self-employment tax. AGI is adjusted gross income. Net profit is what your business earned after expenses. Withholding is tax already taken out of paychecks or pensions. Bracket tax is the income tax from the 2026 rate brackets, where each slice of income is taxed at its own rate. The Social Security part of SE tax stops at $184,500 of earnings.
The safe harbors protect you from the penalty, not from the tax itself. Whatever you still owe is due by April 15, 2027. Many people use last year's tax as their safe harbor, because it's a number they already know. If your income is rising, paying 100% (or 110%) of last year's tax keeps you penalty-free. You'll just owe more in April.
The 2026 due dates are April 15, June 15 and September 15, 2026, and January 15, 2027. None falls on a weekend this year. You can skip the January payment if you file your 2026 return and pay everything you owe by February 1, 2027.
Worked example
A single freelancer expects $60,000 of net profit in 2026, has no wages or withholding, and owed $9,000 of total tax on a 2025 return with AGI of $70,000.
- Self-employment tax: 15.3% × (92.35% × $60,000) = 15.3% × $55,410 = $8,477.73.
- AGI: $60,000 − half of SE tax ($4,238.87) ≈ $55,761.14; taxable income after the $16,100 standard deduction ≈ $39,661.14.
- Income tax: 10% × $12,400 + 12% × $27,261.14 ≈ $4,511.34, so total 2026 tax ≈ $12,989.07.
- Safe harbors: 90% × $12,989.07 = $11,690.16, or 100% × $9,000 = $9,000. The smaller is $9,000.
- Quarterly payment: $9,000 ÷ 4 = $2,250.
Result: Paying $2,250 by each of the four due dates avoids the penalty. About $3,989.07 would still be due by April 15, 2027. Paying $3,247.27 a quarter instead would cover the whole year.
Understanding the result
If your income is uneven, for example if most of it arrives late in the year, a different method can lower your early payments. It's called the annualized income installment method, on Form 2210. This calculator assumes four equal payments.
It helps to set money aside as you earn it. A simple habit: move a fixed share of every payment into a separate account for taxes. Your effective rate in the results is a good share to use.
State income taxes usually have their own estimated payment rules and dates. This calculator covers federal tax only.
Assumptions and limitations
- Tax year 2026. Brackets and the standard deduction come from Rev. Proc. 2025-32. Self-employment tax uses the $184,500 wage base. The safe harbor rules and due dates are the ones printed on the 2026 Form 1040-ES.
- Ordinary income only, with the standard deduction plus any other deductions you enter. Withholding counts as paid evenly over the year.
- Additional Medicare tax (an extra 0.9% on high earnings) uses your filing status's threshold, with wages and self-employment income added together.
- This is an estimate, not tax advice. Form 1040-ES, Publication 505 and a tax professional have the final word.
- It doesn't model capital gains rates, the net investment income tax, the alternative minimum tax, refundable credits or state taxes. You need to enter the qualified business income deduction yourself.
- Farmers and fishermen (who use a 66⅔% rule), household employers and the annualized installment method follow different rules.
Frequently asked questions
When are 2026 estimated tax payments due?
April 15, June 15 and September 15, 2026, and January 15, 2027. A due date that falls on a weekend or legal holiday moves to the next business day. None of them do this cycle.
How do I avoid the underpayment penalty?
Between withholding and estimated payments, pay at least the smaller of two amounts: 90% of your 2026 tax, or 100% of your 2025 tax. That second one is 110% if your 2025 AGI was over $150,000 ($75,000 if married filing separately). Spread the payments across the four due dates. You also owe no penalty if your balance due is under $1,000.
Do I have to pay estimated taxes if I have a W-2 job?
Only if the tax taken out of your paychecks won't cover enough of your tax. Many people with a side business ask their employer to withhold more instead, using a new W-4 form. Withholding counts as paid evenly through the year, so it works even late in the year.
Does estimated tax include self-employment tax?
Yes. Estimated payments cover your whole federal tax bill, not just income tax. That includes the 15.3% self-employment tax for Social Security and Medicare.
What if I underpaid an earlier quarter?
Pay the shortfall as soon as you can. The penalty works like interest, so it grows with each day you're late. Raising later payments or withholding reduces it, but may not remove it for the earlier quarter.
Sources
- IRS Form 1040-ES (2026), Estimated Tax for Individuals (checked 2026-10-19)
- IRS Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-19)
How this calculator is checked
Method: 2026 Form 1040-ES (safe harbors, $1,000 threshold, due dates); 2026 brackets and standard deduction from Rev. Proc. 2025-32; self-employment tax per Schedule SE with the 2026 wage base; Additional Medicare thresholds from IRS Topic 560 (figures in src/lib/finance/tax-2026.ts). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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