Stock Average Calculator
Your average cost per share is the total you paid divided by the total shares you own. Add each buy below to get your average cost (cost basis), total cost, and, if you add the current price, your unrealized profit or loss.
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Try Bullynx freeThe average cost formula
Average cost per share = total cost ÷ total shares
Total cost is the sum of (shares × price) across every buy. Because it is share-weighted, a large purchase pulls the average toward its price more than a small one.
Worked example
You buy in two lots:
- 10 shares at $100 = $1,000
- 15 shares at $90 = $1,350
- Total = 25 shares for $2,350
- Average cost = $2,350 ÷ 25 = $94.00 per share
At a current price of $105, your 25 shares are worth $2,625, an unrealized gain of $275 (about 11.7%). Use it with the position size calculator to plan any further buys against your risk budget.
How to use this calculator
- Enter each buy. Add the number of shares and the price for every purchase you made.
- Add more buys. Use "Add a buy" for each separate purchase at a different price.
- Read your average cost. The tool shows your average cost per share, total shares, and total cost.
- Add the current price (optional). Enter the current price to see your market value and unrealized profit or loss.
Frequently asked questions
How do you calculate the average cost per share?
Add up the total amount spent across every purchase, then divide by the total number of shares owned. The result is your average cost per share, also called your cost basis. It is a weighted average, so larger buys move it more than small ones.
What is cost basis?
Cost basis is the total amount you paid for a holding, including each purchase. Per-share cost basis is that total divided by your share count. It is the reference point for measuring gains or losses and is used for tax reporting in many jurisdictions.
What does averaging down mean?
Averaging down means buying more of a holding after the price has fallen, which lowers your average cost per share. It reduces the price needed to break even, but it also increases your exposure to a position that is already losing, so it carries real risk.
Does this calculator account for fees or taxes?
No. It uses your entered share counts and prices only. Add commissions into a buy price if you want them included, and treat the result as an estimate, not tax advice.
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Educational only. Not financial advice. NFA. This tool does not account for fees or taxes and is not tax advice. Read the full risk disclosure.