Know your real cost basis before you sell

If you buy the same stock multiple times, your average purchase price and the true break-even price can differ. Average price tracks only your weighted cost per share, while break-even also includes trading fees like commission and transaction tax. This calculator aggregates multiple purchases to show both values clearly, plus charts, compare, copy, and PDF export.

Multiple purchase actions Commission and tax per row Break-even and average price Charts, compare, PDF export
Break-even
Includes fees
Average price
Cost basis per share
Guide
Formulas and tips

How to use the calculator

  1. 1

    Add purchase rows

    Click Add purchase for each buy you want to include. Remove any row you do not need.

  2. 2

    Enter shares and cost

    Fill in the number of shares and total cost for each purchase. These must be positive values.

  3. 3

    Enter commission and tax

    Add per purchase commission and tax fees. Use 0 if they do not apply.

  4. 4

    Calculate and review

    Press Calculate to see break-even price, average price, charts, purchase detail table, and optional scenario compare. Export a PDF if needed.

Detailed guide and references▶

Why break-even matters

Average purchase price is useful for tracking your cost basis across multiple buys, but it does not include trading fees. If you want to know the minimum selling price that avoids a loss, you need break-even price, which adds commission and tax.

Stock chart on a monitor
Break-even price includes fees that many traders forget when estimating profit

Formulas

The calculator uses these core formulas:

  • Average purchase price: Total cost divided by total shares.
  • Break-even price: (Total cost + total commission + total tax) divided by total shares.

When you add multiple purchase actions, the tool aggregates shares, cost, and fees across rows and then computes the final per share values.

Factors and fees

Commission fees

Broker commissions increase total cost. They can be flat per trade or per share.

  • Higher commissions raise break-even price.
  • Average purchase price typically ignores commissions unless you fold them into cost.

Tax fees

Some markets apply transaction tax or duties.

  • Tax increases break-even price.
  • Tax is often a percent of transaction value, but this calculator accepts direct amounts per purchase row.

Multiple purchases

More purchases require accurate input for each action, especially when fees differ by trade size.

Example workflow

For each buy, enter:

  • Shares
  • Total cost paid for that buy
  • Commission fee for that buy
  • Tax fee for that buy

After calculation, compare break-even price versus average price. The gap between them is driven by fees. The charts visualize how much of your total outlay is cost versus fees.

Limitations and tips

  • Real broker statements may include additional fees, FX spread, routing fees, or rounding rules.
  • If you want fees included in average price, you can add fees into the cost field manually, but then break-even will double count unless you set fees to zero.
  • Use this tool as an educational reference and verify using your broker records.

FAQs

Are the results exact?▶

They are estimates based on the values you enter. Brokers may apply additional fees, FX spreads, or rounding rules, so confirm with your statements.

What is the difference between average price and break-even price?▶

Average purchase price is total cost divided by total shares. Break-even price adds commission and tax fees on top, so it is usually higher.

Can I add many purchases?▶

Yes. Add rows for each purchase and the calculator will aggregate the totals.

How should I enter fees?▶

Enter commission and tax as direct dollar amounts per row. If your broker reports combined fees, you can enter them as one row fee.

Key takeaways

  • Average purchase price tracks cost basis per share, excluding fees unless you include them in cost.
  • Break-even price includes commission and tax, so it reflects the minimum sell price to avoid a loss.
  • Use multiple purchase rows to reflect real fills and per-trade fee differences.
  • Charts help you see how much of your total outlay is cost versus fees.
  • Use scenario compare and PDF export for quick record keeping and comparisons.

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Calculator

Add purchase rows, enter shares, cost, commission, and tax, then press Calculate

These results are for reference only and may differ from broker statements due to additional fees or rounding rules.