Stock Loss Tax Calculator 2026

The calculator nets short-term gains and losses, nets long-term gains and losses, then combines the two results to estimate net capital gain or loss.

If the final result is a net loss, it applies the annual ordinary-income deduction cap based on filing status and computes potential carryforward loss.

It also estimates federal tax savings from the deductible portion by comparing ordinary income tax before and after the allowable deduction.

That makes the page useful for two very different questions: "How much tax can this loss save me now?" and "How much of this loss do I still carry into a future year?" Those are related, but they are not the same answer.

What Is Tax-Loss Harvesting?

Tax-loss harvesting means realizing investment losses on purpose so they can offset gains and potentially reduce current or future tax liability. In plain language, a losing position can sometimes create tax value even when the investment result itself was disappointing.

That is why good harvesting is never just about "selling losers." It is about deciding whether a realized loss improves your overall after-tax outcome without damaging the portfolio strategy you actually want to keep.

Formula Explained

The basic order is simple: short-term gains and losses are netted together, long-term gains and losses are netted together, and then the two results are combined. If the final answer is still a net loss, the tax code generally allows a limited ordinary-income deduction each year, with the rest carried forward.

That carryforward piece is the part many investors misunderstand. A loss above the annual deduction cap is usually not wasted. It just may not be fully usable in the current year. This calculator makes that distinction visible instead of hiding it inside one tax-savings line.

Examples

Real-Life Applications

• Reviewing year-end capital gains before deciding whether to harvest losses.
• Estimating whether carryforward losses still have planning value in future years.
• Comparing the tax benefit of selling now versus waiting for a different tax year.
• Explaining to a household why a loss can lower taxes without making the investment "good."

Common Mistakes

• Assuming every realized loss creates an immediate full tax deduction.
• Ignoring the difference between short-term and long-term netting.
• Forgetting that wash-sale rules can disrupt the intended tax result.
• Making a tax trade that weakens the portfolio more than it helps the tax bill.

Tips & Best Practices

• Look at gains, losses, and carryforwards together before selling.
• Keep transaction records clean so future carryforward use stays defensible.
• Do not let tax optimization replace portfolio discipline.
• Check wash-sale timing before re-entering a similar position.

If you want to connect stock-loss planning with the rest of your tax picture, use the Capital Gains Tax Calculator, the Federal Income Tax Calculator, and the Tax Refund Calculator next.

Keep the research moving with Missouri Income Tax Calculator, Massachusetts Income Tax Calculator, Georgia Income Tax Calculator, and Illinois Income Tax Calculator.