Capital Gains Tax Estimator

How to use this tool

1. Enter cost basis, sale price, and holding period.
2. Enter taxable income before this gain, filing status, and tax year.
3. See estimated tax owed and net profit.

How this calculator stacks a gain

Enter taxable income after deductions but before the gain entered here, then select the filing status and tax year. The calculator finds the extra federal tax created by adding the gain to that income. It does not multiply the whole gain by the final bracket rate, which would overstate tax whenever a gain crosses a bracket boundary.

Short-term gains (held one year or less) are treated as incremental ordinary income. Long-term gains (held more than one year) fill any remaining 0% long-term-gain band first, then the 15% band, then the 20% band if applicable. The displayed rate is the resulting effective federal tax rate on this gain, not a marginal rate.

2026 long-term capital-gains brackets

These are the default 2026 limits. The calculator also includes 2024 and 2025 tables, so the output remains tied to the selected tax year. IRS long-term-gain thresholds apply after the ordinary taxable income entered in the tool has already occupied its portion of the bands.

Optional Net Investment Income Tax estimate

You can turn on an optional 3.8% Net Investment Income Tax (NIIT) estimate and enter your total modified adjusted gross income (MAGI), including the gain in this calculator. The estimate applies 3.8% to the smaller of the positive gain or the amount by which MAGI exceeds the filing-status threshold: $200,000 for Single or Head of Household, $250,000 for Married Filing Jointly, and $125,000 for Married Filing Separately. These thresholds are not inflation-indexed. MAGI is not inferred from taxable income.

This simplified, single-gain estimate is not Form 8960 preparation: actual NIIT depends on net investment income and other tax details this tool does not collect. The calculator also excludes state tax, the special rules for collectibles and qualified small-business stock, depreciation recapture, primary-residence exclusions, and loss carryforwards.

Wash-sale rule

A loss may be disallowed when you buy a substantially identical security within 30 days before or after its sale. That rule and netting gains against losses can change the gain that belongs in this calculator; determine your net reportable gain before using this single-gain estimate.