Short-term versus long-term, and why it matters
The single biggest factor in your capital gains bill is how long you held the asset. Sell within a year of buying and the profit is a short-term gain, taxed at the same ordinary rates as your wages. Hold for more than a year and it becomes a long-term gain, which qualifies for a separate, gentler set of rates.
The gap is large. An ordinary rate can reach 37%, while the top long-term rate is 20%, and many people pay 15% or even 0% on long-term gains. That difference is exactly why investors so often wait past the one-year mark before selling.
How this calculator figures the tax
For a long-term gain, the tool looks at your other taxable income to decide which band you land in, then applies the matching 0%, 15% or 20% rate to the whole gain. For a short-term gain, it stacks the gain on top of your existing income and measures the extra ordinary tax that addition creates.
That stacking method is what makes the effective rate shown here meaningful: it is the tax divided by the gain, so you can see what slice of the profit actually leaves your pocket.
Practical ways to keep more of a gain
A few levers can lower what you owe, all within ordinary rules:
- Cross the one-year holding line before selling to unlock long-term rates.
- Realise gains in a year when your other income is low, which can drop you into the 15% or 0% band.
- Offset gains with realised losses on other holdings (tax-loss harvesting).
- Hold assets inside tax-advantaged accounts where gains are deferred or never taxed.
What this estimate leaves out
This is a simplified federal model using approximate 2024 figures. It ignores the 3.8% net investment income tax that can apply at higher incomes, state capital gains taxes, the special rules for collectibles and certain real estate, and the interaction of the gain with deductions and credits. Treat the result as a planning estimate, not tax advice — confirm your situation with a qualified tax professional.
Formula
long-term: tax = gain × {0,15,20}% by income. short-term: tax = ordinaryTax(income + gain) − ordinaryTax(income)Frequently asked questions
- Why does my other income matter?
- Long-term rates depend on which income band you fall into, and short-term gains stack on top of your ordinary income, so a higher income can push the gain into a higher rate.