Capital Gains Calculator

How this result is built

Estimate tax on a gain using the long-term bracket you select, with optional 3.8% NIIT.

Long-term capital gains are taxed at 0%, 15%, or 20% depending on taxable income. The thresholds move with inflation, so this page asks you to choose the bracket rather than guess your income from a stale table. The gain is sale proceeds minus cost basis.

What the opening example is for

The 3.8% net investment income tax can stack on top for higher incomes. It is a switch, not an automatic add, because the threshold depends on filing status. Short-term gains are taxed as ordinary income. Use the income tax calculator for those.

The walkthrough below uses the numbers already sitting in Capital Gains Calculator. Press Calculate and the headline should match this page. Then put your own figures in. The math does not run until you press the button, and Clear hides the result.

What each field is doing

The “Cost basis” line on Capital Gains Calculator starts at $8,000.00. Leave that figure only when it matches the statement, the quote, or the plan you are testing. Press Calculate after the edit so the chart and the schedule move with it.

Capital Gains Calculator treats “Sale proceeds” as its own entry, and the form opens with $14,500.00. A round example is useful for learning the page. It is a poor substitute for the number on your own paperwork, so replace it and run the form again.

The remaining fields

Before you replace it, “Long-term rate” reads 15% on Capital Gains Calculator. The other fields stay put while you change this one. That is the clean way to see what this line is doing inside the result.

Look at “Add 3.8% net investment income tax” first if you are checking Capital Gains Calculator: the filled value is No. If the label is a rate, type the annual figure the contract uses. If it is money, type the amount that will actually move, not a rounded hope.

The opening result, line by line

Press Calculate on the opening form and Estimated tax on the gain is $975.00. That is the number the rest of this section is talking about.

Gain is $6,500.00 when you run the opening figures on Capital Gains Calculator. That line is part of the same calculation as the headline. It is not a second balance you can spend on top of the result. Change one input and press Calculate if you want to see whether this line moves.

On this opening pass, rate used is 15.00%. That line is part of the same calculation as the headline. It is not a second balance you can spend on top of the result. Change one input and press Calculate if you want to see whether this line moves.

How those lines were produced

Choose the long-term bracket that matches your taxable income. The 3.8% net investment income tax is optional because it depends on income thresholds.

A second pass changes only “Cost basis”, from $8,000.00 to $8,800.00. Estimated tax on the gain moves from $975.00 to $855.00. Nothing else on the form was edited, so the gap between those two results is the effect of that one field on Capital Gains Calculator. If the gap is tiny, this page is not very sensitive to that entry. If the gap is large, get that entry from a document before you plan around the result.

What this page will not claim

Capital Gains Calculator is a federal estimate from the brackets and inputs written on the page. It is not a tax return. Credits, state tax, and items you do not type are simply absent. Confirm the figure with a filing source before you send money.

Capital Gains Calculator stops at its own formula. When the next question is different, open Income Tax Calculator (2026 federal brackets, without pretending to be a tax return.); Stock Return Calculator (Price gain plus the dividends you were paid.); ROI Calculator (Total ROI and the annualized rate.). Do not add those results to this one as if they were the same kind of dollar.

Check the result before you use it

Start on Capital Gains Calculator by reading the labels, not the headline. The opening labels are Cost basis ($8,000.00), Sale proceeds ($14,500.00), Long-term rate (15%), Add 3.8% net investment income tax (No). If a label is not the fact you have, the result cannot turn into that fact later. The illustration on the form lands on $975.00. When you press Calculate and see that same figure, the button and this explanation are using one formula.

Change one field at a time. Write down the headline, edit a single line, and press Calculate again. A large jump means that line carries the result. A line that does not move is a line the formula ignores, which is a reason to confirm you opened the right page. Capital Gains Calculator is built for one job: A gain, a bracket you choose, and an optional surtax. The description on the page says the same thing in a sentence: Estimate tax on a gain using the long-term bracket you select, with optional 3.8% NIIT.

When the paperwork disagrees

Then hold the headline next to a source outside the site. That source might be a loan estimate, an account statement, a pay stub, or the public limit named in the methodology. A few cents of difference on a long schedule is ordinary rounding. A different rate, a fee you never typed, or a tax the form does not ask for is not rounding. Correct the input. Do not average the page with the paperwork.

When the outside source still disagrees, Capital Gains Calculator has reached the edge of what it will claim. It will not phone a lender, pull a county record, or apply a credit you left blank. Send the calculator name, every input, and the result you expected through the contact page if you think the formula itself is wrong. Until that is settled, read $975.00 as the output of the fields above and nothing else.

FAQs