Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Send each quarter
$7,599
Total estimated tax for the year
$30,398
Self-employment tax
$13,847
Federal income tax
$11,651
State income tax
$4,900
Safe-harbour quarterly amount
$5,250
Pay this and penalties cannot apply
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter projected net self-employment income ($).
- 2Enter filing status.
- 3Enter tax already withheld elsewhere ($).
- 4Enter state income tax rate (%).
- 5Enter last year's total tax ($).
- 6Read your send each quarter on the right — it updates as you type.
- 7Hit Share to keep the scenario or send it to someone.
About this calculator
Freelancers and business owners pay tax four times a year. The safe-harbour rule is simple: pay 100% of last year's tax (110% if you earn over $150,000) and the IRS cannot penalise you no matter what this year brings.
Worked example
Using the values the calculator loads with:
Inputs
- Projected net self-employment income: 98000 $
- Filing status: Single
- Tax already withheld elsewhere: 0 $
- State income tax rate: 5 %
- Last year's total tax: 21000 $
Results
- Send each quarter: $7,599.45
- Total estimated tax for the year: $30,397.79
- Self-employment tax: $13,846.96
- Federal income tax: $11,650.83
- State income tax: $4,900.00
- Safe-harbour quarterly amount: $5,250.00
What each field means
Inputs
- Projected net self-employment income ($)
- The projected net self-employment income used in the calculation, measured in $. Starts at 98000 $ so you have a working example on load.
- Filing status
- Pick the option that matches your situation — the maths changes per option. Choices: Single, Married filing jointly.
- Tax already withheld elsewhere ($)
- The tax already withheld elsewhere used in the calculation, measured in $. Starts at 0 $ so you have a working example on load.
- State income tax rate (%)
- The state income tax rate used in the calculation, measured in %. Starts at 5 % so you have a working example on load. Accepted range: 0–15 %.
- Last year's total tax ($)
- The last year's total tax used in the calculation, measured in $. Starts at 21000 $ so you have a working example on load.
Results
- Send each quarter
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total estimated tax for the year
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Self-employment tax
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Federal income tax
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- State income tax
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Safe-harbour quarterly amount
- Pay this and penalties cannot apply
FAQ
How does the quarterly estimated tax calculator work?
Freelancers and business owners pay tax four times a year. The safe-harbour rule is simple: pay 100% of last year's tax (110% if you earn over $150,000) and the IRS cannot penalise you no matter what this year brings. The underlying maths is: Quarterly payment = (Projected income tax + self-employment tax − withholding) ÷ 4.
What do I need to enter?
5 values: projected net self-employment income, filing status, tax already withheld elsewhere, state income tax rate, and last year's total tax. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the send each quarter result mean?
It is returned as a money amount in US dollars and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
Who is this tool for?
It's built for anyone comparing money scenarios before committing — budgeting a payment, sanity-checking a quote, or seeing what a change in rate or term actually costs.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Quarterly Estimated Tax Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/quarterly-estimated-tax
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/quarterly-estimated-tax" target="_blank" rel="noopener">Quarterly Estimated Tax Calculator — RevenueLab</a> (2026).</p>
Source: [Quarterly Estimated Tax Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/quarterly-estimated-tax) (2026).