Stock Average Cost Calculator
Average price per share across several buys, with break-even price and unrealized gain.
Schedule
About this calculator
Your average cost is the total you paid for a stock — including commissions — divided by the number of shares you own. It is also your break-even price: above it the position shows a gain, below it a loss. Buying more below your average (averaging down) lowers it; buying above it raises it.
Worked example
Buy 100 shares at $50, 50 at $42 and 80 at $38.50 and you've paid $10,180 for 230 shares — an average cost of $44.26 a share. At $45 the position is worth $10,350, a gain of $170 (1.7%).
Average cost and taxes
For taxes, your broker tracks each purchase lot separately. Unless you choose specific lots, the shares you sell are treated as the first ones you bought (first in, first out), and the average-cost method is allowed only for mutual fund shares and shares bought through dividend reinvestment plans. So the taxable gain on a partial sale can differ from the average shown here.
Averaging down
Adding to a losing position lowers your break-even price, but it also puts more money into the same stock, and it pays off only if the price recovers. Decide in advance how large any one position may grow.
Sources: IRS Publication 550.
Results are estimates for planning and education, assume constant rates, and ignore taxes and fees unless stated. Not financial advice.
Frequently asked questions
How do I calculate my average cost per share?
Add up what you paid for every purchase, including commissions, and divide by the total number of shares. For example, 100 shares at $50 ($5,000) plus 100 at $40 ($4,000) is $9,000 for 200 shares — an average of $45.
What is my break-even price?
Your average cost per share, including purchase fees: sell above it and you make money, below it you lose. If selling will cost a commission too, add that amount divided by your shares.
Should commissions be included in cost basis?
Yes. Commissions and other purchase costs are part of your cost basis, which lowers your taxable gain when you sell. Many brokers no longer charge commissions on US stock trades, so this is often zero.