What the gain is worth after tax

A gain on something held a year or less is short-term and taxed at your ordinary income rate, the same as wages. Held longer than a year, it becomes long-term and is taxed at the separate capital gains rates of 0%, 15% or 20% depending on income. The gap is large enough that the sale date can matter more than the sale price: on the same profit, the difference between month eleven and month thirteen is often several percentage points of the whole gain.

It is an additional 3.8% on investment income once your income passes $200,000 filing single or $250,000 filing jointly. It applies to the lesser of the gain itself or the amount by which you cross the threshold, so a gain that straddles the line is only partly exposed. It sits on top of the capital gains rate rather than replacing it, which is why a long-term gain for a high earner is often taxed at 23.8% federally rather than 20%.

Enough to rival the federal bill. A handful of states levy no broad income tax and so take nothing from the gain. Several tax it as ordinary income at rates that reach into the double digits. Others exclude part of a long-term gain outright, and Washington takes no income tax but applies a separate 7% excise to long-term gains above a threshold. The calculator carries every state and notes the unusual ones as you select them.

It is built for comparing choices, not for filing. It uses 2025 federal brackets and each state's top marginal rate, and it deliberately leaves out state brackets below that top rate, local and city taxes, deductions, losses carried forward, and anything held inside a retirement account. Filing status is limited to single or married filing jointly. Treat it as a way to see the shape of the decision, and take the actual number to an accountant.