How the 2026 Capital Gains Estimate Works
A gain on an asset held for more than one year is generally treated as a long-term capital gain and can fall into the 0%, 15%, or 20% federal rate bands. The calculator stacks the gain on top of the other income you enter so a single gain can span more than one long-term capital-gain band.
Short-term gains are modeled using ordinary 2026 federal income-tax rates. The estimator also applies the 3.8% Net Investment Income Tax using the lesser of modeled investment income or the amount by which modified adjusted gross income exceeds the applicable threshold.
Capital-gains tax calculations become more complicated when a transaction is not just one purchase followed by one sale. Multiple tax lots, wash-sale adjustments, carried losses, special asset rules and state tax can all change the final liability. Use the calculator to understand the federal treatment represented by its inputs, especially the difference between short- and long-term treatment, then reconcile the result with your actual cost basis and tax records before filing.
Frequently Asked Questions
When is a capital gain long term?
For this estimator, a gain is treated as long term when the asset has been held for more than one year; shorter holding periods are modeled as short-term gains taxed at ordinary federal rates.
Does exceeding the NIIT threshold make the entire gain subject to 3.8%?
Not necessarily. NIIT is generally based on the lesser of net investment income or the excess of modified adjusted gross income over the applicable threshold.
Why can my broker's taxable gain differ from sale price minus what I remember paying?
Cost basis can include commissions, reinvested distributions, tax-lot selection and adjustments such as wash sales. The taxable basis in your records may therefore differ from the original cash purchase amount.
Methodology & Related Tools
Review how RatioCalc builds, tests and updates calculator models before using an estimate for a material decision.
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