Estimated Tax Calculator 2026
Calculate your quarterly estimated tax payments. Use the safe harbor rule to avoid underpayment penalties.
How to Use This Calculator
Tab "Quarterly Payment"
Enter your expected total income for 2026, filing status, and any deductions above the standard deduction. If you have W-2 income with tax already withheld, enter that amount so the calculator subtracts it from your obligation. If you are self-employed, enter your net self-employment income to include SE tax (15.3%) in the estimate. The result shows your total estimated tax, how much remains after withholding, and the quarterly payment amount with all four due dates.
Tab "Safe Harbor"
The safe harbor rule lets you avoid underpayment penalties by paying a minimum amount regardless of your actual tax owed. Enter your last year's total tax (Form 1040, line 24) and last year's AGI. The calculator computes two thresholds: 90% of this year's estimated tax and 100% of last year's tax (110% if prior AGI exceeded $150,000). Your safe harbor amount is the lower of the two, divided into quarterly payments.
Tab "Penalty Risk"
Enter your actual quarterly payments made (or planned) for each quarter. The calculator compares each payment to the required amount derived from the safe harbor rule, computes the underpayment per quarter, and estimates the IRS penalty at approximately 8% annualized. Earlier underpayments accrue more penalty because the money is late for a longer period.
The Formulas
Taxable income = Total income − Standard deduction − Additional deductions
Single: $15,750 · MFJ: $31,500 · HoH: $23,500
Tax = Sum of (taxable income in each bracket × bracket rate)
Brackets: 10%, 12%, 22%, 24%, 32%, 35%, 37%
Self-Employment Tax:
SE earnings = Net SE income × 92.35%
Social Security = 12.4% × min(SE earnings, $184,500)
Medicare = 2.9% × SE earnings
Additional Medicare = 0.9% × max(0, SE earnings − $200,000)
Half of SE tax is deductible from federal income
Quarterly Estimated Payment:
Total estimated tax = Federal income tax + SE tax − Tax credits
Remaining = Total estimated tax − W-2 withholding
Quarterly payment = Remaining ÷ 4
Safe Harbor (avoid penalty):
Method A = 100% of last year's tax (110% if prior AGI > $150K)
Method B = 90% of this year's estimated tax
Safe harbor = Lower of Method A and Method B
Underpayment Penalty:
Penalty per quarter = Underpayment × IRS rate (~8%) × Period fraction
Period fraction = Time from due date to filing date (Apr 15 next year)
Q1 underpayment accrues ~9 months of interest, Q4 accrues ~0-3 months
Example
$100,000 Income — Single, $15,000 W-2 Withholding
In this example, the $15,000 in W-2 withholding exceeds the $13,624 estimated federal tax, so no quarterly estimated payments are needed. However, if you had $30,000 in self-employment income on top of your salary (and no additional withholding), your SE tax would add roughly $4,238, bringing your total liability to ~$17,862. After $15,000 withholding, you would owe $2,862, or about $716 per quarter.