Capital Gains Tax Calculator

Capital gains tax is the tax you pay on profit from selling an investment — and the difference between paying it at the short-term rate versus the long-term rate can be 10 to 20 percentage points on the same gain. That rate difference changes investment holding decisions in meaningful ways: a gain that looks identical in dollar terms can result in wildly different after-tax proceeds depending entirely on whether you held the asset for 12 months and one day versus 11 months. Understanding how capital gains tax is calculated, how the holding period affects your rate, and which strategies legally reduce what you owe is material to every investment decision you make in a taxable account.

Net Investment Income Tax and State Taxes

Federal capital gains tax is only part of the picture. Most states tax capital gains as ordinary income — California at 13.3%, New Jersey at 10.75%, Oregon at 9.9%, New York at 10.9%. A few states have no income tax (Florida, Texas, Washington, Nevada, Wyoming, South Dakota, Alaska) and thus no state capital gains tax. This geographic reality creates meaningful after-tax return differences for investors in high-tax states.

Combined federal and California taxes on a $50,000 long-term capital gain for a taxpayer in the 20% federal long-term rate bracket: 20% federal + 3.8% NIIT + 13.3% California = 37.1% effective tax rate. The same gain in Florida: 20% + 3.8% = 23.8%. The state difference alone costs $6,650 on a $50,000 gain. Over an investing lifetime, residency decisions have compounding tax implications that dwarf most other financial choices.

Capital Gains in Retirement Accounts

Assets held in traditional IRAs and 401(k)s don't generate capital gains events when you buy or sell within the account. All growth accumulates tax-deferred, and you pay ordinary income tax only on withdrawals in retirement. In Roth accounts, qualified withdrawals are completely tax-free — making Roth accounts ideal for holding your highest-growth, highest-gain assets.

The practical asset location strategy: hold tax-inefficient assets (high-dividend stocks, REITs, actively managed funds with high turnover) in tax-sheltered retirement accounts. Hold tax-efficient assets (index ETFs with low turnover, buy-and-hold individual stocks, municipal bonds) in taxable accounts where their low capital gains distributions create minimal annual tax drag. This location strategy can increase after-tax portfolio returns by 0.3 to 0.7% per year without any change in investment selection — purely through tax placement.

Short-Term vs Long-Term Capital Gains

Assets held for one year or less generate short-term capital gains, which are taxed at ordinary income tax rates — the same rates as your salary and wages. In 2024, those brackets run from 10% to 37%. Assets held for more than one year generate long-term capital gains, which have preferential rates: 0%, 15%, or 20% depending on taxable income and filing status.

For a single filer in 2024: long-term capital gains rate is 0% for taxable income up to $47,025. It's 15% for income between $47,026 and $518,900. It's 20% for income above $518,900. High earners also face the Net Investment Income Tax (NIIT) of 3.8% on investment income above $200,000 (single) or $250,000 (married filing jointly), making the effective maximum long-term rate 23.8% for top earners.

The practical implication: a person in the 22% income bracket who sells a stock held 11 months with a $15,000 gain pays 22% = $3,300 in tax. Wait one month more: if their income is below $47,025 after standard deductions, they owe $0 on that same gain. If their income puts them in the 15% long-term bracket: $2,250. The one-month wait saves $3,300 or saves $1,050 — simply by timing the sale.

Tax-Loss Harvesting to Offset Gains

Tax-loss harvesting — intentionally selling investments at a loss to offset capital gains — is one of the most reliable legal tax reduction strategies available. Rules: capital losses offset capital gains of the same type first (short-term losses offset short-term gains, long-term losses offset long-term gains). Excess losses of either type can offset gains of the other type. If total losses exceed total gains, up to $3,000 in net capital losses can be deducted against ordinary income per year, with remaining losses carrying forward indefinitely.

If you have $12,000 in realized long-term capital gains and you identify a position with a $12,000 unrealized long-term loss, selling it produces $12,000 in losses that directly offset your gains — a $12,000 gain × 15% = $1,800 tax eliminated. The wash-sale rule prevents you from immediately repurchasing the same security — you must wait 31 days before repurchasing or substitute a different but economically similar investment. The wash-sale rule applies per security: you can sell Vanguard Total Market ETF (VTI) at a loss and immediately buy Schwab Total Market ETF (SCHB) to maintain market exposure without triggering the wash sale.

Calculating Your Capital Gain

Capital gain = Sale proceeds - Cost basis - Transaction costs. Sale proceeds are what you received. Cost basis is what you paid for the asset, including purchase commissions. Transaction costs (selling commissions, if any) reduce your gain. If you bought 100 shares at $45.00 per share (total $4,500) and sold at $78.50 per share (total $7,850): Capital gain = $7,850 - $4,500 = $3,350. If you paid $4.95 in commissions buying and $4.95 selling: Capital gain = $7,850 - $4,500 - $4.95 - $4.95 = $3,340.10.

For dividend reinvestment shares, each reinvestment purchase creates a separate lot with its own cost basis and purchase date. If you bought an initial 100 shares and reinvested dividends to accumulate 40 additional shares across 8 separate reinvestment dates, you have 9 separate tax lots to track. When you sell, you choose which lots to sell first — this matters enormously for minimizing gains or strategically realizing losses.

Lot Selection Strategy: Minimizing Gain

When you sell partial positions (not your entire holding), you choose which shares to sell. The default method in most brokerages is First In, First Out (FIFO) — oldest shares sell first. But you can specify specific lots, and this choice dramatically affects your tax bill.

Jennifer, 42, in San Diego, California holds 200 shares of a technology stock. She bought 100 shares in 2019 at $42.00 (current value: $127.50, long-term, $8,550 unrealized gain). She bought another 100 shares in 2023 at $118.00 (current value: $127.50, short-term, $950 unrealized gain). She needs to sell 100 shares. FIFO default: sell the 2019 shares, realizing $8,550 long-term gain. Specific lot identification: sell the 2023 shares, realizing only $950 short-term gain. At her 22% marginal rate: FIFO creates $8,550 × 15% (long-term) = $1,282.50 in tax. Lot identification creates $950 × 22% (short-term) = $209 in tax. The lot choice saved $1,073.50 — a 84% tax reduction on that transaction.

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