Calculate your average cost per share across multiple purchases at different prices.
How It Works
How Stock Average (Cost Basis) Calculator Works
Each purchase lot contributes its own cost (shares times price), and the calculator divides the total amount spent across all lots by the total number of shares owned — a weighted average, so a larger purchase pulls the average price more toward its own price than a smaller one does.
Worked Example
See It In Action
Buying 10 shares at $100 and later another 10 shares at $120 gives an average cost basis of $110 per share across all 20 shares.
FAQ
Frequently Asked Questions
Why is this called "cost basis"?
Cost basis is the term used for tax purposes — it's what you subtract from the sale price to determine your taxable capital gain or loss when you eventually sell.
What if I sold some shares in between purchases?
This calculator only handles purchase lots — if shares were sold and rebought, work out the cost basis of the remaining shares first using your brokerage's accounting method (like FIFO), then enter just the lots that are still currently held.
