Formulas and 2026 figures checked & updated: July 2026
Used for the safe harbor target
How to Use the Quarterly Estimated Tax Calculator
- Enter your expected net self-employment income for the year (after business expenses, before self-employment tax).
- Select your filing status.
- Enter any W-2 withholding you already have coming out of a day job, plus any other taxable income.
- Enter your state tax rate and last year's total tax liability to see your safe harbor target.
- Review your total self-employment tax, total estimated tax, and quarterly payment.
What This Calculator Does
This calculator estimates the total tax a self-employed or 1099 worker owes for the year — self-employment tax plus federal income tax plus state tax — and divides the balance (after any W-2 withholding) into four quarterly payments.
It also computes the IRS safe harbor target, the minimum you need to pay through the year via withholding and estimated payments combined to avoid an underpayment penalty, regardless of what you ultimately owe when you file.
Formula
Quarterly Payment = (Total Estimated Tax − Withholding) ÷ 4- SE Tax15.3% on 92.35% of net SE income (12.4% capped + 2.9% uncapped)
- Safe HarborSmaller of 90% this year's tax or 110% last year's tax
Examples
Example: $80,000 net SE income, single filer, no W-2 withholding
5% state tax rate.
Self-employment tax ≈ $11,300; combined with federal and state income tax, the quarterly payment lands around $5,700 in this scenario — actual figures shift with deductions and other income.
Methodology
Self-employment tax: 92.35% of net SE income is subject to 12.4% Social Security (up to the wage base) and 2.9% Medicare (uncapped), plus 0.9% Additional Medicare Tax above the filing-status threshold. Half of total SE tax is deducted before calculating federal income tax, which uses the same 2025 brackets and standard deduction as our income tax calculator. Quarterly payment = (total estimated tax − withholding) ÷ 4. Safe harbor target = the smaller of 90% of this year's estimated tax or 110% of last year's liability.
Frequently Asked Questions
What is the self-employment tax rate?+
15.3% total — 12.4% for Social Security (up to the annual wage base) and 2.9% for Medicare (uncapped), applied to 92.35% of your net self-employment earnings. An additional 0.9% Medicare surtax applies above $200,000 (single) or $250,000 (married filing jointly).
What is the safe harbor rule?+
You generally avoid an underpayment penalty if, through withholding and estimated payments combined, you pay at least 90% of this year's total tax liability or 100% of last year's liability (110% if last year's AGI was over $150,000) — whichever of those two targets is smaller.
When are quarterly estimated taxes due?+
Typically April 15, June 15, September 15, and January 15 of the following year — though exact dates shift slightly when they fall on a weekend or holiday. Check the current IRS calendar each year.
Is half of my self-employment tax really deductible?+
Yes. Half of your total self-employment tax is deductible when calculating your adjusted gross income for federal income tax purposes — this calculator applies that deduction automatically before computing your income tax.
Do I need to make quarterly payments if I also have a W-2 job?+
Not necessarily — if your W-2 employer withholds enough extra tax to cover your self-employment income (you can increase withholding via a new W-4), you may be able to skip separate quarterly payments entirely. This calculator accounts for W-2 withholding you enter as a credit against your total liability.
Can I save my results?+
Yes. Use “Save results” to store a snapshot. Without an account it remains in this browser. If you log in, saved scenarios sync securely to your SmartRates account so they are available on your other devices.
How do I share my calculation?+
Click “Share” in the toolbar to copy a link (or open your device’s share sheet). The link encodes your exact inputs, so whoever opens it sees the calculator pre-filled with the same numbers and the same result.
Can I email my calculator results?+
Yes. Click “Email results” to open your default email application with the current inputs, results, and calculator link already included. Review the message and choose the recipient before sending.
Can I export or print my results as a PDF?+
Yes. Click “Export PDF” to open a clean, printable summary of your inputs and results that you can save as a PDF or print. It includes a timestamp and a link back to the calculator.
How accurate are the calculator results?+
The arithmetic follows the formula and assumptions documented on this page. The result is still an estimate because actual rates, fees, taxes, timing conventions, eligibility rules, and provider calculations can differ. Use figures from your official quote, statement, contract, or tax form before making a financial decision.
Which inputs have the biggest effect on the result?+
Rate, time, starting balance, recurring payments or contributions, and fees usually have the largest effects. Change one input at a time to create a conservative, expected, and optimistic scenario instead of relying on a single forecast.
Are taxes, fees, and inflation included?+
Only when they appear as an input or are explicitly described in the methodology. Do not assume an omitted cost is zero. Review the formula and methodology sections to see exactly what is included before comparing the result with an outside quote.
Can this calculator predict future rates or returns?+
No. A calculator projects the assumptions entered; it cannot predict market returns, inflation, variable interest rates, tax-law changes, or provider decisions. Rerun the calculation with several assumptions to understand the range of possible outcomes.
Why might my lender, bank, broker, or tax software show a different result?+
Professional systems may use daily timing, transaction dates, compounding conventions, rounding rules, account-specific fees, credits, eligibility details, or regulations that a general-purpose calculator cannot know. A small difference can be rounding; a large difference usually means an assumption or included cost is different.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.