Capital Gains Tax Calculator

When you sell a stock, cryptocurrency, piece of real estate, or any other capital asset for a profit, you typically owe federal capital gains tax on that profit. Understanding how much tax you will owe — before you sell — helps you plan smarter: timing your sale to qualify for lower long-term rates, estimating the after-tax proceeds you will actually receive, or deciding whether to harvest a loss to offset gains elsewhere. This capital gains tax calculator estimates your 2025 federal tax liability in seconds.

Step 1: Enter Your Purchase and Sale Prices

Enter the original purchase price (your cost basis) and the sale price (your proceeds) in the corresponding fields. The cost basis is what you paid for the asset, including any commissions or fees. The sale price is what you received when you sold it, before deducting costs. The calculator determines your capital gain or loss from the difference.

Step 2: Select Your Holding Period and Asset Type

Choose whether you held the asset for more than one year (long-term) or one year or less (short-term). This is the most important factor in determining your capital gains tax rate. Long-term gains qualify for the preferential 0%, 15%, or 20% rates. Short-term gains are taxed as ordinary income, at the same rates as wages — which can reach 37% for high earners. Also select your asset type (stocks, crypto, real estate, or other), which provides context for your results.

Step 3: Enter Your Filing Status and Taxable Income

Your filing status and total taxable income determine which capital gains bracket applies to your gain. Enter your filing status (single, married filing jointly, married filing separately, or head of household) and your estimated taxable income for the year, including the gain from this sale. Taxable income is your gross income minus deductions — use last year's tax return or your best estimate. These fields are needed to apply the correct 2025 long-term capital gains thresholds and to check whether the 3.8% Net Investment Income Tax (NIIT) surcharge applies.

Understanding Your Results

After clicking Calculate, the tool shows your capital gain or loss, the tax rate applied, the estimated tax owed, and your net proceeds — the amount you keep after paying federal tax. If your income exceeds the NIIT threshold ($200,000 for single filers, $250,000 for married filing jointly), the 3.8% surcharge is added automatically and shown separately in the breakdown. The effective rate on your gain is the total tax owed divided by the gain, giving you a true picture of what percentage of your profit goes to taxes.

Long-Term vs Short-Term: Why It Matters

The difference between long-term and short-term capital gains tax rates can be enormous. For a single filer with $100,000 in taxable income who sells an asset for a $30,000 gain, a short-term gain would be taxed at 22% (as ordinary income), resulting in roughly $6,600 in tax. The same gain as a long-term gain would be taxed at just 15%, saving over $2,100. Holding an investment just one day longer — crossing the one-year mark — can result in thousands of dollars in tax savings for large gains. Always consider the holding period before selling.