THE NUMORIX GUIDE
How to use the Capital Gains Tax Calculator
Last reviewed September 14, 2026
What this calculator does
The engine finds gain = sale price - purchase price.
Formula and method
The engine finds gain = sale price - purchase price. A nonpositive gain produces zero tax. Otherwise it classifies a holding period of at least one year as long-term, selects its embedded filing-status bracket table, computes bracket tax on annual income plus the gain, subtracts tax on annual income alone, and reports the difference as tax on the gain.
Variables and inputs
Enter Purchase Price, Sale Price, Holding Period in years, Filing Status, and Annual Income. The status choices are Single, Married Filing Jointly, and Head of Household. Dollar values are not adjusted for basis additions, selling costs, state tax, or a separate tax year field.
Worked example
For a $50,000 purchase, $80,000 sale, three-year holding period, single filing status, and $75,000 annual income, gain = $30,000 and the route selects long-term treatment. Its embedded brackets produce tax on $105,000 minus tax on $75,000 of about $4,500, an effective rate of 15% on the gain.
How to interpret the result
The result is the incremental federal-style tax from adding the entered gain to the entered income under the route's bracket table. It is not simply gain multiplied by one rate in every case, because a gain can cross bracket thresholds and short-term gains use the ordinary-income table.
Common mistakes to avoid
Use adjusted tax basis rather than an unadjusted purchase price when the real transaction includes reinvested dividends, improvements, or prior depreciation. Count the holding period correctly, select the actual filing status, and enter income in dollars rather than a tax rate.
Assumptions and limitations
The bracket thresholds are hardcoded and the UI has no tax-year selector. The engine excludes federal net investment income tax, state and local tax, exemptions, deductions, losses, collectibles, depreciation recapture, selling expenses, wash-sale rules, and special assets. It is not a tax return or filing recommendation.