Stock Loss Calculator

Calculate your stock losses, tax deduction potential, and capital loss carryforward. Understand how losses offset gains for tax planning.

SC
Written by Sarah Chen, CFP
Certified Financial Planner
JW
Fact-checked by Dr. James Wilson, PhD
Options Strategy Researcher
Profit & LossFact-Checked

Input Values

$

Price per share at purchase.

$

Current price or sale price.

Number of shares.

$

Total capital gains from other sales this tax year.

%

Your federal marginal tax bracket.

Results

Total Loss
$0.00
Percentage Loss
0.00%
Gains Offset$0.00
Ordinary Income Deduction$0.00
Estimated Tax Savings$0.00
Results update automatically as you change input values.

Understanding Stock Losses

Stock losses, while never desirable, can serve a valuable tax purpose. In the US, capital losses can offset capital gains dollar for dollar, and up to $3,000 in net capital losses can be deducted against ordinary income each year. Any remaining losses carry forward indefinitely to future tax years.

Tax-loss harvesting, the strategy of intentionally realizing losses to offset gains, is a powerful tax planning tool. This calculator helps you quantify your losses and understand their tax impact.

Stock Loss Calculation
Loss = (Purchase Price - Sale Price) × Shares
Where:
Purchase Price = Original price per share
Sale Price = Price at which shares were sold
Shares = Number of shares sold
Tax Savings from Loss
Tax Savings = Deductible Loss × Tax Rate
Where:
Deductible Loss = Amount of loss that offsets gains or income
Tax Rate = Your marginal tax rate
Stock Loss and Tax Impact Example
Given
Purchase Price
$85
Sale Price
$52
Shares
100
Other Gains
$5,000
Tax Bracket
24%
Calculation Steps
  1. 1Total Loss = ($85 - $52) × 100 = $3,300
  2. 2Percentage Loss = $3,300 / $8,500 = 38.8%
  3. 3Gains Offset = min($3,300, $5,000) = $3,300
  4. 4Remaining gains = $5,000 - $3,300 = $1,700 (still taxable)
  5. 5No excess loss for ordinary income deduction
  6. 6Tax Savings = $3,300 × 24% = $792
Result
The $3,300 stock loss offsets $3,300 of the $5,000 in other capital gains, saving approximately $792 in federal taxes. The remaining $1,700 in gains is still taxable.

Tax-Loss Harvesting Rules

Capital Loss Tax Rules (US)
RuleDetailLimitCarryforward
Offset capital gainsLosses offset gains dollar for dollarUnlimitedN/A
Offset ordinary incomeNet losses deduct from ordinary income$3,000/year ($1,500 married filing separately)Indefinite
Wash sale ruleCannot rebuy same security within 30 daysN/ALoss is disallowed, added to new cost basis
Long vs. short matchingShort losses offset short gains first, then longN/AUnused losses carry character

Tax-Loss Harvesting Strategy

1
Identify Losing Positions
Review your portfolio for positions with unrealized losses. These are candidates for tax-loss harvesting.
2
Calculate Tax Benefit
Multiply the potential loss by your tax rate to estimate savings. A $5,000 loss at 24% bracket saves $1,200.
3
Sell and Replace
Sell the losing position and replace it with a similar (but not substantially identical) investment to maintain market exposure while realizing the loss.
4
Avoid Wash Sales
Do not repurchase the same security within 30 days before or after the sale. Buy a different ETF or stock in the same sector instead.
!
The Wash Sale Rule

If you sell a stock at a loss and buy the same or substantially identical security within 30 days before or after the sale, the loss is disallowed. The disallowed loss is added to the cost basis of the new shares. This applies across all your accounts, including IRAs.

  • Capital losses have no expiration date; unused losses carry forward indefinitely
  • Married couples filing jointly share the $3,000 ordinary income deduction limit
  • Short-term losses are more valuable tax-wise because they offset short-term gains taxed at higher rates
  • Consider tax-loss harvesting in December to offset current-year gains
  • Unrealized losses are not deductible; you must sell to realize the loss for tax purposes

Frequently Asked Questions

Capital losses offset capital gains dollar for dollar. If losses exceed gains, up to $3,000 per year can offset ordinary income. Remaining losses carry forward indefinitely. A $3,300 loss with $5,000 in gains reduces taxable gains to $1,700.

Sources & References

  • U.S. Securities and Exchange Commission (SEC) - Investor Education
  • Options Clearing Corporation (OCC) - Options Education
  • Chicago Board Options Exchange (CBOE) - Options Strategies
  • Hull, J.C. "Options, Futures, and Other Derivatives" (11th Edition, 2021)

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