Stock Average Calculator

Work out the weighted average cost per share or unit across several purchase lots, including transaction fees. Add, edit, reorder and remove lots, and optionally enter a current price yourself to see position value and unrealised gain or loss.

Finance Runs client-side Free to use

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About the Stock Average Calculator

Stock Average Calculator combines several purchases of the same share, fund unit or other holding into one weighted average cost. For each lot, enter the quantity, the price per unit and, if you like, the fee you paid. The tool shows total units, total invested including fees, total fees, the average cost per unit including fees and the average purchase price excluding fees.

You can also type in a current price to see the current position value and the unrealised gain or loss in money and as a percentage. That price is whatever you enter; the tool never looks up live market data. Taxes, selling fees, dividends, stock splits, bonus issues and other corporate actions, currency conversion and fractional-unit rules are not modelled.

How to use

Enter the quantity and price per unit for your first purchase, and any fee.
Add a row for each further purchase; reorder or remove rows as needed.
Optionally type in a current price per unit.
Click Calculate to see the averages, totals and lot table.
Copy the summary, download it, or download the lots as CSV.

Key features

Lot editor for up to 100 purchases: add, edit, reorder and remove.
Weighted average cost including fees, and average price excluding fees.
Total units, total invested and total fees.
Optional manually entered current price for value and unrealised gain/loss.
Lot table with CSV download.
Display-only currency symbol.
Copy Summary, Download CSV, Download Summary, Reset and Back.

Best practices

Enter each purchase exactly as shown on your contract note or statement.
Include the fees you actually paid so the average reflects your true cost.
Adjust quantities and prices yourself after splits or bonus issues.
Keep separate calculations for different holdings or accounts.
Check tax treatment with a qualified professional; it is not included here.

Benefits

Quick, accurate weighted averages without a spreadsheet.
Clear separation of costs with and without fees.
No market-data lookup, so it works offline and stays private.
Private: nothing is uploaded or stored.

Frequently asked questions

How is the average cost calculated?

Each lot’s cost is quantity × price + fee. The average cost per unit is the total of all lot costs divided by the total number of units. The tool also shows the average price excluding fees.

Is the current price live?

No. The current price is only what you type in. The tool does not connect to any exchange or data feed.

What does unrealised gain or loss mean?

It is the difference between the current value (units × the price you entered) and the total amount you invested including fees. It is not realised until units are sold, and selling costs and taxes are not included.

Can I enter fractional quantities?

Yes. Quantities can include decimals, for example mutual fund units. Whether fractional units can be bought or sold depends on the product and is not checked.

What about stock splits and bonus shares?

They are not adjusted automatically. After a split or bonus issue, adjust the quantities and prices yourself, or add a lot with the bonus units at a price of 0.

Does averaging down make a holding better?

The tool only calculates averages. Whether to buy, hold or sell is your decision; a lower average cost does not change the risk of the holding.

Is my information saved or sent anywhere?

No. Every calculation runs in your browser. The numbers you enter and the results are not uploaded, not looked up online and not saved in browser storage. Reset clears them from the page.