Estimate the US federal tax on a capital gain for tax year 2025: long-term gains are stacked on top of your ordinary income and taxed in slices at 0%, 15% and 20%, short-term gains are estimated at your marginal ordinary rate, and the 3.8% Net Investment Income Tax is added when it applies. Add a flat state rate for a rough state estimate. Everything updates live in your browser — nothing is uploaded. Rates checked 29 October 2026 — US tax year 2025.
Rates checked 29 October 2026 — US tax year 2025. Long-term thresholds and ordinary brackets: IRS Revenue Procedure 2024-40 and IRS Topic No. 409 (capital gains). NIIT: 3.8% on the lesser of your gain or the amount by which the income total used here passes $200,000 (single / head of household) or $250,000 (married filing jointly) — statutory thresholds, IRS Topic No. 559. This calculator treats your entered income total as the MAGI figure for that test, which is a simplification.
The long-term gain is stacked on top of your ordinary income: the slice of the gain that still fits under the 0% threshold is taxed at 0%, the next slice up to the 15% ceiling at 15%, and anything above that ceiling at 20%. The short-term estimate uses the single marginal rate described on the left — your real short-term tax is worked through the ordinary brackets on Schedule D, so treat that line as an estimate, not a filing figure.
Ordinary income fills the lower thresholds first. Whatever room is left in each band is what your long-term gain can use at that rate.
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Estimate US federal capital gains tax for tax year 2025 — long-term gains stacked at 0%, 15% and 20%, short-term gains at your marginal rate, plus the 3.8% NIIT and an optional state estimate.
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Estimate US federal capital gains tax for tax year 2025 (rates checked 29 October 2026): enter your filing status, your taxable ordinary income excluding the gain, your long-term and short-term gains and an optional flat state rate, and see the long-term gain stacked slice by slice at 0%, 15% and 20%, a short-term estimate at your marginal rate, the 3.8% Net Investment Income Tax when it applies, and the effective rate on your gains.
Single filer, $40,000 of taxable ordinary income and a $10,000 long-term gain, tax year 2025. The 0% ceiling for a single filer is $48,350 (IRS Topic No. 409), so ordinary income fills $40,000 of it and leaves $48,350 − $40,000 = $8,350 of 0% room: $8,350 of the gain is taxed at 0%. The remaining $10,000 − $8,350 = $1,650 sits in the 15% band and is taxed at $1,650 × 15% = $247.50. Nothing reaches the 20% band (which starts above $533,400 for single filers), total income of $50,000 is far under the $200,000 NIIT threshold, so the total federal tax is $247.50 — an effective rate of 2.48% on the gain. Rates checked 29 October 2026 — US tax year 2025.
Long-term gains stack on top of ordinary income: the slice of the gain that still fits under the maximum zero-rate amount ($48,350 single / $96,700 married filing jointly / $64,750 head of household for 2025, IRS Revenue Procedure 2024-40 and Topic No. 409) is taxed at 0%, the next slice up to the maximum 15% amount ($533,400 / $600,050 / $566,700) at 15%, and the rest at 20%. Short-term gains are taxed as ordinary income; as a stated simplification this calculator taxes the whole short-term portion at the marginal ordinary bracket your total income reaches (2025 brackets, Revenue Procedure 2024-40), rather than slicing it through each bracket. The NIIT is 3.8% of the lesser of your total gains or the amount by which your income total (used here as the MAGI figure) exceeds $200,000 single or head of household / $250,000 married filing jointly (IRS Topic No. 559). The state line is simply your entered flat rate × total gains.
For tax year 2025 the 0% rate applies up to taxable income of $48,350 for single filers, $96,700 for married filing jointly and $64,750 for head of household. The 15% rate then applies up to $533,400 (single), $600,050 (joint) and $566,700 (head of household), and 20% applies above those amounts (IRS Topic No. 409, Revenue Procedure 2024-40).
Because the thresholds are measured on total taxable income, not on the gain alone. If your ordinary income is $40,000 as a single filer, the first $8,350 of a long-term gain still fits under the $48,350 ceiling and is taxed at 0% — only the rest of the gain moves into the 15% band.
Short-term gains (assets held one year or less) are ordinary income. As a plainly stated simplification, this calculator taxes the whole short-term portion at your marginal bracket — the top 2025 ordinary bracket your total income reaches. On a real return the gain is worked through the brackets, so the estimate can run a little high when the gain straddles a bracket boundary.
The Net Investment Income Tax is an extra 3.8% on investment income, including capital gains, when your modified adjusted gross income passes $200,000 (single or head of household) or $250,000 (married filing jointly). It applies to the lesser of your net investment income or the amount by which MAGI exceeds the threshold — this calculator uses your entered income total as the MAGI figure and says so on the page.
Only if you enter a state rate: the calculator multiplies your total gains by that flat percent as a rough estimate. Some states tax gains exactly like ordinary income, a few have special capital gains provisions, and some tax no income at all — check your state before relying on the figure.
No — on the gain only: sale price minus your adjusted basis (usually what you paid, plus certain costs). Enter the profit, not the sale price, in the gain boxes.
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