Tax estimate calculator

Tax year 2026. Federal plus California or New York: ordinary and capital-gains brackets, qualified dividends, the Additional Medicare tax, AMT, itemized-vs-standard, the safe-harbor test, the underpayment penalty, and the per-paycheck fix. This is the app's own tax engine compiled to WebAssembly and run in your browser: nothing you type leaves this tab.

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What you need. The most recent paystub for each job — yours and, if you file jointly, your spouse's — plus, if you have them, this year's 1099s and last year's Form 1040. start here marks what the estimate hinges on; everything else refines it. Blank means zero. The result updates as you type; there is no button.

Who is filing — filing status and state set the standard deduction and the bracket thresholds.
Paystubs — one card per job with its year-to-date column, pay date and pay frequency. The engine projects each to December — salary by the calendar, vests and bonuses by their schedule — and shows the projection under the card. Edit the forecast line if you know better.
Other income and payments — investment income and estimated payments for the year, and last year's return for the safe-harbor test.

Who is filing

Sets the standard deduction and where each bracket starts. Filing jointly opens a second set of paystubs for your spouse.

Filing status start here State start here California and New York are modeled in full. Elsewhere, choose "Federal only": the state part is simply not estimated. Age 65 or older (0–2)You, then your spouse — born before January 2, 1962, as on Form 1040. Each adds to the standard deduction (and in California a $158 credit); a spouse counts on a joint return only. Blind (0–2)You, then your spouse, as on Form 1040. Each adds to the standard deduction (and in California a $158 credit); a spouse counts on a joint return only.

Paystubs start here

One card per job, from its most recent paystub: the year-to-date column, the pay date, and how often it pays. Salary and withholding are projected to December by the calendar; vests and bonuses by their own schedule. No paystub? Tick "full-year totals" and enter the year's figures instead.

You

Other income for the year

Full-year estimates: what you have so far plus what you expect by December.

Taxable interest1099-INT box 1. Ordinary dividends1099-DIV box 1a. of which qualified1099-DIV box 1b: taxed at the lower capital-gains rates. Net short-term capital gainSales of holdings kept a year or less; negative for a net loss. Net long-term capital gainHoldings kept over a year; negative for a net loss. The … loss limit is applied. Self-employment net profitSchedule C profit. Self-employment tax and its half deduction are computed for you. Taxable retirement distributions1099-R box 2a: IRA, 401(k) and HSA amounts taxed as ordinary income.

Itemized deductions — only if they might beat the standard deduction (… single, … joint)

The estimate takes whichever is larger. State income tax withheld and SDI from your paystubs already count; enter the rest here.

Property tax and other state and local taxes paidOutside payroll: property tax, estimated state payments. The 2026 cap (…, phasing down above … of income) is applied to the total. Mortgage interestForm 1098 box 1. Charitable giftsCash and property. The …-of-income floor is applied. Medical expensesOut-of-pocket total. Only the part above … of income counts. Other itemizedAnything else on Schedule A.

Incentive stock options (AMT)

ISO exercise bargain element this year(Fair value − strike) × shares exercised and not sold this year. This is what triggers the alternative minimum tax.

Paid outside payroll

Withholding comes from the paystubs above; this is the rest.

Estimated payments madeForm 1040-ES payments sent this year, all quarters together.

Safe harbor from last year's return (optional)

With these, the estimate can tell whether you are already safe from the underpayment penalty on the prior-year rule (100%, or … above … of income — … married filing separately). Without last year's tax it tests only the 90%-of-this-year rule; with the tax but not the income, it takes the higher ….

Last year's total federal taxForm 1040 line 24. Last year's adjusted gross incomeForm 1040 line 11.

What this is

The same engine the app runs, compiled to WebAssembly. Every line in "how it was computed" is a rule the engine applied, and every assumption it lists is one it makes for the app too. New York City and Yonkers taxes are not modeled; neither are credits beyond the ones the engine derives, foreign income, or part-year residency, which the app handles from your actual records.

The app does the rest: paystub and broker imports, actual vest timing, dated Form 2210 / FTB 5805 penalty math, what-if scenarios, and the W-4 and DE-4 per-paycheck numbers with your real cadence. On your computer; we never see it.

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