How to Use the Capital Gains Tax Estimator
This tool is built around the real U.S. federal capital gains system, not a translation of Korea's proposed financial investment income tax. Korea's version was designed around a flat ~50 million KRW annual exemption and a flat 22%/27.5% rate. The U.S. system has no such blanket exemption — instead, your rate depends entirely on how long you held the asset and your total taxable income for the year.
Gains on assets held one year or less (short-term) are taxed as ordinary income, using the same brackets as your wages — up to 37% at the top. Gains on assets held over one year (long-term) get preferential rates of 0%, 15%, or 20% depending on your income, which is why many investors deliberately hold winning positions past the one-year mark.
Enter your gain, choose short-term or long-term, and enter your other taxable income for the year (2024 single-filer brackets are used) — the calculator stacks the gain on top of your income to find the marginal rate that applies and estimates the tax. This is a simplified approximation using 2024 single-filer thresholds; it doesn't account for the Net Investment Income Tax (an extra 3.8% for high earners), state taxes, or married-filing brackets, so treat it as a planning estimate rather than a filing-ready number.
Frequently Asked Questions
Assets held one year or less are taxed as short-term gains at your ordinary income rate (up to 37%), while assets held over one year qualify for long-term capital gains rates, which top out at 20% — a major incentive to hold investments longer.
No. Korea's proposed system used a flat ~50 million KRW annual exemption then a flat 22%/27.5% rate. The U.S. system works completely differently — no blanket exemption, and the rate depends on your holding period and total taxable income. This calculator uses the real U.S. bracket structure, not a direct translation.
Capital losses can offset capital gains, and up to $3,000 of net losses can offset ordinary income per year, with the rest carried forward. This calculator assumes a gain — enter 0 if your position is a net loss, since no tax is owed.