Short vs Long Term Capital Gains Tax Calculator

A capital gains tax calculator estimates the tax you owe when you sell an asset for more than you paid, and it shows how that tax changes depending on how long you held the position. On this page the calculator sits above this text: you enter your sale proceeds, your cost basis, whether the holding was short term or long term, your marginal tax rate, and the long term rate that applies to you, and it returns your capital gain, the tax owed, your net proceeds after tax, the rate applied, and your effective rate. The single most important factor is time. In the United States, an asset held for one year or less is a short term gain taxed as ordinary income, while an asset held for more than one year is a long term gain taxed at the lower 0, 15, or 20 percent brackets. This guide explains every input, walks through worked examples, and shows the current figures for the 2025 and 2026 tax years so you can sanity check the numbers before you file.

How the capital gains tax calculator works

The calculator above turns five inputs into five outputs. Understanding each field keeps your estimate honest. Enter real numbers from your trade log, not rounded guesses, because small differences in cost basis can move you across a bracket line.

• Sale Proceeds: the total amount you received when you sold, after any commissions or fees are subtracted. This is your gross exit value.
• Cost Basis: what you originally paid to acquire the asset, including commissions and any adjustments. Accurate basis is where most mistakes start, so keep records.
• Holding Period: a simple short or long choice. Short means one year or less. Long means more than one year, measured from the day after purchase to the sale date.
• Your Marginal Rate: the tax rate on your next dollar of ordinary income. For short term gains this is the rate that applies, because short term gains are taxed like wages.
• Long Term Rate: the 0, 15, or 20 percent figure that applies to your long term gains based on your taxable income and filing status.

The outputs then read as follows. Capital Gain is Sale Proceeds minus Cost Basis, and it can be negative, which is a capital loss. Tax Owed is the gain multiplied by whichever rate applies. Net After Tax is the gain minus the tax, meaning the money you actually keep. Rate Applied confirms which rate the tool used, either your marginal rate for short term or your selected long term rate. Effective Rate is the tax owed divided by the gain, expressed as a percentage, which lets you compare scenarios at a glance.

The one year line: short term versus long term

The tax code draws a hard line at one year. If you sell on or before the one year anniversary of your purchase, the gain is short term. If you sell even one day after that anniversary, it is long term. The holding period starts the day after you buy and includes the day you sell. Because the difference in rate can be large, the exact sale date matters. A trader who sells at day 364 can pay a much higher rate than one who waits until day 366 on the same gain. The calculator lets you flip the Holding Period input so you can see both outcomes side by side before you decide to close a position.

How short term gains are taxed as ordinary income

Short term capital gains do not get a special rate. They are added to your other taxable income, such as wages and business profit, and taxed at the ordinary federal brackets. For the 2025 and 2026 tax years those brackets run 10, 12, 22, 24, 32, 35, and 37 percent. Where a gain lands depends on your total income, so a large short term gain can even push part of your income into a higher bracket. This is why active traders who close positions quickly often face the steepest tax bills. Your marginal rate input in the calculator represents this ordinary rate. State income tax, where it applies, sits on top of these federal figures and is not modeled here.

How long term gains use the 0, 15, and 20 percent brackets

Long term gains are rewarded with three preferential rates: 0 percent, 15 percent, and 20 percent. Which one applies depends on your total taxable income and your filing status, not on the size of the gain alone. Many taxpayers with moderate income pay 15 percent. Lower income taxpayers can pay 0 percent on gains that fall inside the 0 percent band, and high income taxpayers pay 20 percent on gains above the top threshold. The table below shows the 2025 taxable income thresholds by filing status as an illustration. Treat these as a reference to verify, because the IRS adjusts them for inflation each year and the 2026 figures will differ.

The 3.8 percent Net Investment Income Tax for high earners

On top of the capital gains rate, some taxpayers owe the Net Investment Income Tax, known as NIIT. It is an extra 3.8 percent on net investment income, which includes capital gains, when your modified adjusted gross income rises above a threshold. For 2025 and 2026 those thresholds are commonly cited as $200,000 for single filers, $250,000 for married filing jointly, and $125,000 for married filing separately. These thresholds are not indexed for inflation, so more people cross them over time. When it applies, a 20 percent long term gain effectively becomes 23.8 percent, and a 37 percent short term gain can reach 40.8 percent. The calculator above does not add NIIT automatically, so if you are near or above these income levels, plan for the extra 3.8 percent yourself and confirm it with your preparer.

Three worked examples with real numbers

Example 1: a short term gain taxed as income

Suppose you buy a position for a cost basis of $9,000 and sell it five months later for sale proceeds of $12,000. Your capital gain is $12,000 minus $9,000, which equals $3,000. Because you held for five months, this is short term and taxed at your marginal rate. If that rate is 24 percent, the tax owed is $3,000 times 0.24, which is $720. Your net after tax is $3,000 minus $720, which is $2,280. The effective rate is $720 divided by $3,000, which is 24 percent. Short term gains and marginal rate move together.

Example 2: the same trade held past one year

Now take a larger position. You buy for a cost basis of $18,000 and sell more than one year later for sale proceeds of $30,000, giving a capital gain of $12,000. Because you held more than one year, it is long term. If your income puts you in the 15 percent long term bracket, the tax owed is $12,000 times 0.15, which is $1,800. Net after tax is $10,200 and the effective rate is 15 percent. Compare that with selling the same $12,000 gain short term at a 24 percent marginal rate, which would cost $2,880. Waiting past the one year line saved $1,080 in tax on this single trade.

Example 3: a high earner facing NIIT

Consider a single filer with modified adjusted gross income of $250,000 who realizes a long term gain of $40,000. That income places the gain in the 20 percent long term bracket, so the base tax is $40,000 times 0.20, which is $8,000. Because the income is above the $200,000 NIIT threshold, an extra 3.8 percent applies, adding $40,000 times 0.038, which is $1,520. Total tax is $9,520, net after tax is $30,480, and the effective rate is $9,520 divided by $40,000, which is 23.8 percent. This shows why very high earners feel the combined bite.

Why holding longer can cut the rate, and how tax loss harvesting helps

Holding longer can lower your rate because it moves a gain out of the ordinary brackets and into the preferential long term brackets. The gap can be more than 20 percentage points for high income traders, as Example 2 showed. This does not mean you should hold a losing or overvalued position just to save tax, since a falling price can cost you far more than the tax saved. Tax should inform the decision, not drive it. Tax loss harvesting is the practice of selling losing positions to realize losses that offset your realized gains. If you have a $12,000 gain and also sell a position at a $5,000 loss, your net taxable gain drops to $7,000. If losses exceed gains, you can generally deduct up to $3,000 of net capital loss against ordinary income per year and carry the rest forward, though you must respect the wash sale rule, which disallows a loss if you buy a substantially identical asset within 30 days before or after the sale. Confirm these mechanics with a professional, because they carry specific conditions.

1. Check the holding period before you sell, because crossing the one year line can lower the rate.
2. Match realized losses against realized gains in the same year to shrink the taxable amount.
3. Watch the 30 day wash sale window so a harvested loss is not disallowed.
4. Estimate whether your income triggers the 3.8 percent NIIT and add it to your plan.
5. Set aside the estimated tax from each closed trade so you are not surprised at filing time.

Common mistakes to avoid

• Forgetting to add commissions and fees to cost basis, which overstates the gain and the tax.
• Assuming all gains get the low long term rate when a position was actually held one year or less.
• Ignoring your total taxable income, which decides whether your long term rate is 0, 15, or 20 percent.
• Overlooking the 3.8 percent NIIT when income is near the threshold.
• Selling and rebuying inside the wash sale window and losing the deduction.
• Treating this calculator output as a filing figure rather than an estimate to verify.

Accurate tax estimates start with an accurate record of every trade: entry date, exit date, cost basis, and proceeds. When your log is clean, filling in the calculator above takes seconds and your numbers hold up at tax time. That is the discipline OneTradeJournal is built for. Keep a clear, dated log of each position as you close it, and you will spend less time reconstructing basis and more time reviewing whether your holding decisions actually served your plan. No tool can promise a lower bill, but a well kept journal makes tax season calmer and your review of each trade more honest.