Quarterly Estimated Tax Calculator (Form 1040-ES)

Your inputs

What to send the IRS

Tax year

Filing status

Net self-employment earnings

Expected profit for the whole year after business expenses — the bottom line of Schedule C.

W-2 wages

Salary from a job, if you have one alongside the freelance work. It uses up part of the Social Security wage base first.

Federal tax withheld this year

What a job or pension will withhold across the whole year. Withholding counts toward the requirement, so it reduces the instalments.

Last year’s return, and other income

Last year’s total tax

Total tax on last year’s return, not the balance you paid in April. Leaving it blank means only the 90%-of-this-year test can be used.

Last year’s AGI

Above the statutory threshold the safe harbour rises from 100% to 110% of last year’s tax.

Other ordinary income

Interest, non-qualified dividends, pension income — taxed at ordinary rates with no payroll tax attached.

Your inputs are calculated locally and are not stored.

Each quarterly payment$5,014.75

Four payments of $5,014.75 meet the 90%-of-this-year safe harbour for 2026.

Projected total tax: $22,287.77
Self-employment tax: $12,716.60
Federal income tax: $9,571.17
Adjusted gross income: $83,641.70
Marginal rate: 22%
Deductible half of SE tax: $6,358.30

2026 payment schedule — Form 1040-ES
Period covered	Due	Amount
1 January – 31 March 2026	15 April 2026	$5,014.75
1 April – 31 May 2026	15 June 2026	$5,014.75
1 June – 31 August 2026	15 September 2026	$5,014.75
1 September – 31 December 2026	15 January 2027	$5,014.75

$2,228.78 would still be owed at filingThe safe harbour avoids the underpayment penalty; it does not pay the tax. Paying the four instalments above leaves this much to settle with the return, so it is worth setting aside.

The four instalments are equal because this assumes income arrives evenly through the year. If yours is lumpy — a big autumn project, say — the annualised-income method on Form 2210 can shift the instalments to match, and it is not computed here.

Federal tax only. State, city and local income taxes are not included, so unless you live in one of the states with no income tax, your real total is higher than this.

Every 2026 figure used above, and the document it was read from:

IRS Topic No. 751 — Social Security and Medicare withholding rates verified 28 July 2026
IRS — Questions and answers for the Additional Medicare Tax verified 28 July 2026
IRS — Estimated taxes verified 28 July 2026
IRS Publication 505 — Tax Withholding and Estimated Tax verified 28 July 2026
IRS — Self-employment tax (Social Security and Medicare taxes) verified 28 July 2026
SSA 2026 cost-of-living adjustment fact sheet verified 27 July 2026
IRS Rev. Proc. 2025-32 verified 27 July 2026

Formula & methodology

How an estimated payment is worked out

Self-employment tax comes first, because half of it is deductible before income tax is calculated. Then the two are added, the smaller of the two safe-harbour tests decides what has to be paid through the year, withholding is credited against it, and what is left is split four ways.

SE base = Net earnings × 92.35%
SE tax = min(SE base, Wage base − W-2 wages) × 12.4% + SE base × 2.9%
AGI = W-2 wages + Other income + Net earnings − ½ SE tax
Income tax = brackets applied to (AGI − Deduction)
Required = min(90% × This year, Prior-year % × Last year)
Each quarter = max(Required − Withholding, 0) ÷ 4

92.35%: 100% less the employer-equivalent FICA share, derived from the two cited rates rather than hard-coded
Wage base: The Social Security ceiling, used up by W-2 wages first
Prior-year %: 100%, or 110% when last year’s AGI was above the statutory threshold

There is no clock anywhere in this. Which year you are paying for is a choice you make above, and the due dates come from the data module with their IRS citation — including the years where a deadline lands on a weekend and moves to the following Monday.

Worked example

$80,000 of freelance profit

The self-employment base is 80,000 × 92.35% = $73,880. Because that is below the Social Security wage base and there are no W-2 wages using it up, the full base carries 12.4% Social Security and 2.9% Medicare: $11,303.64 of self-employment tax, of which $5,651.82 is deductible before income tax. These figures are pinned by unit tests.

Income tax is then calculated on what is left, and the two are added to get the projected total. With no prior-year figure entered, only the 90% test is available, so the requirement is 90% of that total and each quarter is a quarter of it.

Assumptions

What this calculator assumes

Income earned evenly across the year, so the four instalments are equal. Form 2210’s annualised-income method is not computed.
Net earnings are already net of deductible business expenses, and the home-office, QBI and health-insurance deductions are not modelled — each would lower the figure.
The standard deduction unless you enter an itemised total, and no tax credits.
Withholding counts in full toward the requirement whenever in the year it happened, which is how the IRS treats it.
Federal only. Most states require their own estimated payments on their own schedule.
Meeting the safe harbour avoids the penalty, not the tax. Any remaining balance is shown rather than hidden.

The rest of the picture

Self-employment tax calculator — the SECA half on its own, with the deductible portion.
Federal income tax calculator — the income-tax half, bracket by bracket.
Effective tax rate calculator — what the combined bill works out to as a share of income.
Take-home pay calculator — the employee comparison, where the employer pays half the payroll tax for you.

Common questions

Quarterly estimated tax FAQ

What is the safe harbour, and why does it matter more than the exact tax?

The underpayment penalty is not charged if your payments through the year reach either 90% of this year's tax or 100% of last year's (110% if last year's AGI was above the statutory threshold). You pay whichever is smaller. That matters because last year's tax is a number you already know, while this year's is a forecast — so the prior-year test lets you be certain of avoiding a penalty even if you end up earning far more than expected.

If I pay the safe harbour, am I done?

No, and this is the trap. Meeting the safe harbour avoids the penalty; it does not pay the tax. If you earn much more this year than last, the four instalments can be well below what you actually owe, and the difference is due with your return in April. The calculator shows that remaining balance rather than letting it be a surprise.

Do I have to make estimated payments at all?

Not if your tax after withholding comes to less than the statutory minimum, which the calculator checks for you. Withholding from a job or a pension counts toward the requirement no matter when in the year it happened, so an employee with a modest side income can often cover everything by adjusting their Form W-4 instead of sending quarterly payments.

Why are the four payments equal?

Because this assumes income arrives evenly through the year, which is what the standard instalment method also assumes. If your income is lumpy — a large project in the autumn, say — the annualised-income method on Form 2210 lets the instalments follow the income instead. That method is not computed here.

How is self-employment tax worked out?

You are taxed on 92.35% of net earnings, which is the statutory adjustment for the employer-equivalent half of FICA that an employee never pays tax on. Social Security at 12.4% applies to that base up to the wage base — reduced by any W-2 wages, which use the base up first — and Medicare at 2.9% applies to all of it. Half of the result is then deducted before income tax. Below $400 of taxable base no self-employment tax is due at all.

Are state estimated payments included?

No. Most states with an income tax require their own estimated payments, often on the same calendar, and nothing on this site computes them. Budget for those separately.

Primary sources

Sources and review notes

Every rate, threshold and due date used above carries its own citation and verification date, shown beside the result. Formula implementation is covered by deterministic unit tests. No tax professional review is claimed yet.