What tax will I owe on my gains?

2025 US capital gains: long-term gains stacked on ordinary income, short-term taxed as income, plus NIIT — the math tax software shows you only after you pay for it.

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Federal LTCG tax
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Short-term tax (federal)
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NIIT (3.8%)
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Total federal + state
How are long-term gains taxed?Long-term gains are stacked ON TOP of ordinary income. In 2025 single filers: 0% up to $48,350 of taxable income (gains included), 15% to $533,400, 20% beyond. Net investment income tax (NIIT) adds 3.8% above $200k ($250k married).
Why is the same $50k gain taxed so differently for different people?Because gains fill the bracket after your salary. $50k of gains on top of a $30k salary starts at 0%; the same gains on top of a $90k salary start at 15%. That stacking is the part people get wrong.
What about the 0% bracket — can I use it?Yes: single filers in the 0% LTCG bracket can harvest gains and pay nothing federal. A common strategy is harvesting in a low-income year — this tool lets you see exactly where your gains land.
Is this financial advice?No — an educational estimate under 2025 federal law as of writing. Use it to plan; confirm with your preparer before realizing large gains.