Free Quarterly Estimated Tax Calculator

The tax system expects to be paid as income is earned, not once a year. Employees do that without thinking about it, through withholding from every paycheck. When clients pay you directly, nothing is withheld, so the IRS expects you to send it yourself, in four estimated payments spread through the year.

For the 2026 tax year, the payments are due April 15, June 15 and September 15, 2026, and January 15, 2027. Each one covers both income tax and self-employment tax on the profit you expect to make. If you expect to owe $1,000 or more for the year after withholding and refundable credits, you generally have to make them.

The hard part is the amount. You’re paying tax on a year that hasn’t finished, on a profit you can only estimate. This calculator gives a planning estimate of your 2026 federal tax from your expected profit and filing status, then works out the yearly amount that meets the IRS safe harbor and splits it into four payments.

The calculator follows the shape of the 2026 Form 1040-ES worksheet, simplified.

1. Self-employment tax on your profit: 15.3% of 92.35% of net profit, with the Social Security part capped at the $184,500 wage base for 2026.
2. Adjusted gross income = business profit + wages + other income − half of the self-employment tax.
3. Taxable income = adjusted gross income − the 2026 standard deduction for your filing status − any other deductions you enter.
4. Income tax from the 2026 tax rate schedules.
5. Total federal tax = income tax + self-employment tax (+ Additional Medicare Tax if your earnings are high enough).
6. Required for the year = the smaller of 90% of that total, or your 2025 total tax (110% of it if your 2025 adjusted gross income was over $150,000, or $75,000 married filing separately).
7. Each quarterly payment = the required amount, less any tax withheld from wages, divided by four.

Step 6 is the safe harbor. Pay at least that much, on time, and you generally avoid the underpayment penalty, even if you owe more when you file.

A single contractor with no other income

A single contractor expects $85,000 of profit for 2026 and has no other income.

• Self-employment tax: $85,000 × 0.9235 × 0.153 = $12,010.12
• Adjusted gross income: $85,000 − $6,005.06 = $78,994.94
• Taxable income: $78,994.94 − $16,100 = $62,894.94
• Income tax: $5,800 + 22% of the amount over $50,400 = $8,548.89
• Total federal tax: $20,559.01, about 24% of profit

With no 2025 figure entered, the safe harbor is 90% of this year’s tax, $18,503.11, so each quarterly payment is $4,625.78. If the contractor’s 2025 total tax was $14,000, paying 100% of last year’s tax is the smaller safe harbor, and each payment drops to $3,500.

A married couple with a W-2 job

A remodeler expects $110,000 of profit. Her spouse earns $52,000 in wages with $4,800 withheld, and they file jointly. The calculator estimates $15,542.51 of self-employment tax and $16,270.32 of income tax on $122,028.74 of taxable income, $31,812.83 in all.

Ninety percent of that is $28,631.55. Their 2025 tax was $18,500, and their 2025 adjusted gross income was over $150,000, so the prior-year safe harbor is 110%: $20,350. That’s the smaller figure. Less the $4,800 already withheld, they need $15,550 in estimated payments, $3,887.50 a quarter.

Profit that arrives late in the year

A deck builder earns most of the year’s profit between May and September. Four equal payments based on the full year would mean paying in April for work that hasn’t happened. The annualized income installment method, explained in IRS Publication 505, can lower the early payments to match when the income came in; it’s claimed with Form 2210 and its Schedule AI when the return is filed.

The penalty for underpaying is charged on each payment that was short, for the number of days it stayed unpaid. Two targets keep you clear of it in most situations.

The prior-year safe harbor is popular with growing businesses, because the number is already on last year’s return and doesn’t move as the year goes on. The catch: you still owe the rest when you file. Set the difference aside as you earn it.

The 2026 Form 1040-ES lists the ways to pay. Online, you can pay through your IRS online account or IRS Direct Pay from a bank account, or through the Electronic Federal Tax Payment System, EFTPS, once you’re enrolled. You can pay by debit or credit card, online or by phone, through a card service provider. Or you can mail a check with a payment voucher from the form.

Whichever way you pay, keep the confirmation with the date and amount, and note which quarter it was for. When you file, you’ll enter the total estimated payments for the year, and the confirmations are your proof.

If you file jointly, payments can be made jointly for both of you. If your situation changes partway through the year, a big job or a slow season, re-run the estimate and change the remaining payments.

Leaving out self-employment tax. Income tax alone can understate the bill by thousands. The payments have to cover both.

Paying once at the end. A single payment in January doesn’t fix underpayments for April, June and September. Each one is measured separately.

Using last year’s safe harbor without saving the rest. It avoids the penalty, not the tax. If profit doubled, so does the balance due in April.

Never re-running the estimate. A big job, a slow summer or a new truck changes the year. Run it again before each due date.

Mixing tax money with operating money. Money set aside for taxes and spent on materials isn’t there when the payment is due.

Taxes are a cost of being self-employed, and like overhead they have to come out of your prices. A rate that pays a fair wage before tax may not after a quarter of it goes to the IRS. Work out what you need to take home, add the taxes on top, and price the work so the business earns it.

The self-employment tax calculator breaks out the 15.3% on its own. Business mileage and equipment both lower your profit, so the mileage calculator and the depreciation calculator feed this estimate too. The break-even calculator shows how many jobs a month cover your fixed costs, your own pay included.

BuildWell builds every estimate with your overhead and markup on top of local wages and material prices, and its invoice list shows totals by day, week or month with paid and unpaid filters, so you can see what came in before each due date.