Stock Average Price Calculator
Find your average cost per share across multiple purchases.
Please note: For information only, not investment advice. Share prices can fall as well as rise and past performance does not predict future results.
What the Stock Average Price Calculator does
Your average cost per share is total money spent divided by total shares held — a share-weighted average, not a simple mean of the prices you paid. It is the level the price must exceed for the position to be in profit.
Formula
Average cost = Σ(Price × Shares) ÷ Σ(Shares)Unrealised P&L = (Current price − Average cost) × Total shares
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Purchase prices | text | Yes | Separate values with commas, spaces or new lines. |
| Shares bought | text | Yes | One quantity per price, in the same order. |
| Current price | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Currency.
- Enter Purchase prices and Shares bought.
- Optionally add Current price.
- Select Calculate.
Worked example
Three buys: 100 at $45.20, 150 at $38.75, 200 at $33.50.
- Prices
- 45.20, 38.75, 33.50
- Shares
- 100, 150, 200
Total cost $17,032.50 for 450 shares — an average of $37.85.
Reading the result
- The "share of position" column shows how much each individual buy actually moves the average — a large early purchase can dominate the figure even if later buys were at very different prices, so the average alone can hide how concentrated the cost basis is.
Assumptions and limitations
- This assumes every share entered is still held — it has no concept of partial sales, so if any shares were sold between purchases, the true remaining cost basis differs from this calculation.
- Commission on each purchase is not included in cost unless it was manually folded into the entered price — unlike the stock profit/loss calculator, there are no separate commission fields here.
Common mistakes
- Treating this average-cost figure as your tax-reportable cost basis without checking whether your jurisdiction actually uses average-cost accounting — some require FIFO or specific-lot identification, which can produce a different number for the same trades.
- Mismatching the two lists — prices and share counts are paired by position, not re-sorted, so entering them out of alignment silently attributes the wrong price to the wrong quantity since the calculator only checks that the lists are the same length.
Frequently asked questions
Is averaging down a good strategy?
It lowers your break-even but concentrates more money in a position already moving against you. It works when the original reasoning still holds and compounds losses when it does not.
Does this match my broker cost basis?
Close, but brokers include commission in cost basis and may use FIFO rather than average cost. Check which method your jurisdiction requires for tax.