What is the Net Investment Income Tax (NIIT)?

An additional 3.8% federal tax on investment income (including capital gains) for single filers with modified adjusted gross income above $200,000 ($250,000 married filing jointly). It's not included in this calculator's estimate — if your total income is near or above that threshold, budget for it separately.

Does this include state capital gains tax?

No — this is federal only. Many states tax capital gains as ordinary income at their own rates, and a few have no state income tax at all, so your total liability depends heavily on where you live.

Why does 'other income' matter for a capital gain?

Long-term capital gains rates are determined by your total taxable income, not the gain in isolation — the IRS stacks your ordinary income first, then layers the capital gain on top to see which bracket(s) it falls into.

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Finance

Capital Gains Tax Calculator

Estimate federal tax on a short- or long-term investment gain.

🔒 Runs entirely in your browser — nothing here is ever uploaded

Last reviewed 2026-08-25

About the Capital Gains Tax Calculator

Estimates federal tax owed on an investment gain, based on whether you held the asset short-term (taxed as ordinary income) or long-term (taxed at the lower 0%/15%/20% capital gains rates), stacked on top of your other taxable income for the year.

How to use it

Enter the Sale price and Cost basis (what you originally paid, plus any improvements).
Enter your Other taxable income for the year — this determines which bracket the gain stacks into.
Choose whether you held the asset Long-term (over 1 year) or Short-term (1 year or less).
Read the estimated tax, effective rate, and net proceeds in the result panel.

Formula

Gain = sale price − cost basis

Long-term gains use the 2026 single-filer capital-gains brackets — 0% up to $49,450 of total income, 15% from $49,450 to $545,500, 20% above — applied only to the portion of the gain that falls in each bracket after your other income fills the brackets below it.

Short-term gains (held ≤1 year) are taxed as ordinary income, using the same 2026 single-filer federal brackets as this site's Income Tax Calculator, stacked the same way on top of your other income.

Worked example

A $20,000 long-term gain on top of $85,000 of other income falls entirely in the 15% bracket for a single filer in 2026, since $85,000 is already above the $49,450 threshold and $105,000 total stays under $545,500 — so the estimated tax is $3,000.

Interpreting your result

Single-filer federal figures only — married-filing-jointly thresholds are higher, and state capital gains taxes (where they apply) aren't included. High earners may also owe the 3.8% Net Investment Income Tax on top of this estimate; see the FAQ.

Recommendations

• Holding an asset past the one-year mark before selling, if you can, moves the gain from ordinary rates (up to 37%) to the much lower long-term rates — often the single biggest lever you control.
• Cost basis includes more than the purchase price — reinvested dividends and capital improvements (for property) increase your basis and reduce your taxable gain, so keep records.
• A capital loss on another investment sold the same year can offset a gain (tax-loss harvesting) — not modeled here, but worth exploring with a tax professional if you're carrying losses.

Frequently asked questions

Long-term means you held the asset for more than one year before selling; short-term means one year or less. The distinction matters a lot — long-term gains get the preferential 0/15/20% rates, while short-term gains are taxed at your full ordinary income rate, which can be more than double.