US Capital Gains Tax Calculator

How it works

Your gain is (sell price − buy price) × shares. How it's taxed depends on how long you held: more than 365 days is long-term, taxed at the preferential 0% / 15% / 20% rates; 365 days or fewer is short-term, taxed at your marginal ordinary income rate.

For a long-term gain, enter your taxable income excluding this gain. The gain then stacks on top of that income across the brackets, so a gain that spans a threshold is split (part at 0%, part at 15%, and so on) rather than taxed at a single flat rate. The headline rate shown is the resulting blended rate.

An optional flat state rate is applied on top. A loss (gain ≤ 0) produces zero tax here. This is a back-of-envelope estimate: it ignores the 3.8% Net Investment Income Tax, wash-sale rules and capital-loss offsets or carryforwards.

Worked example

Buy 100 shares at $50 and sell at $90, held 800 days (long-term), filing single with $100,000 taxable income excluding the gain (so the $4,000 gain stacks into the 15% band) and a 5% state rate:

• Gain = ($90 − $50) × 100 = $4,000.
• Federal tax = $4,000 × 15% = $600; state tax = $4,000 × 5% = $200.
• Total tax = $800; effective rate = $800 / $4,000 = 20%.
• Net proceeds = $90 × 100 − $800 = $8,200; after-tax gain = $3,200.

The formula

term         = "long" if holding_period_days > 365 else "short"
gain         = (sell_price − buy_price) × shares
short term:  federal_tax = max(gain, 0) × marginal_ordinary_rate
long term:   federal_tax = stack the gain on taxable_income (excl. gain)
             across the 0 / 15 / 20% bands, summing tax per band
federal_rate = federal_tax / max(gain, 0)          (blended; 0 if gain ≤ 0)
state_tax    = max(gain, 0) × state_rate
total_tax    = federal_tax + state_tax
net_proceeds = sell_price × shares − total_tax
effective_rate = total_tax / gain   (0 if gain ≤ 0)

FAQ

What's the difference between long-term and short-term?

Holding more than 365 days qualifies for the preferential long-term rate (0%, 15% or 20%). Holding 365 days or fewer is short-term and taxed at your ordinary marginal income rate.

How is my long-term rate chosen?

Enter your taxable income excluding this gain; the gain stacks on top across the 2026 brackets for your filing status (0% below the first threshold, 15% up to the second, 20% above), so a gain spanning a threshold is split across rates. The rate shown is the resulting blended rate.

Does this include state tax or NIIT?

You can add a flat state rate. It does not include the 3.8% Net Investment Income Tax, wash-sale rules or loss carryforwards. It's an estimate, not tax advice.

Who pays the 3.8% NIIT?

The Net Investment Income Tax adds 3.8% on investment income, including capital gains, for higher earners, above roughly $200,000 modified AGI (single) or $250,000 (married filing jointly). These thresholds are not inflation-adjusted. This tool does not add it, so add 3.8% yourself if you are over the threshold.

What is the 0% capital gains bracket?

For the 2026 tax year, long-term gains are taxed at 0% federal if your taxable income is up to $49,450 (single) or $98,900 (married filing jointly); above that it is 15%, then 20% at the top bracket.