Stock Average Calculator
Add each purchase to get your average cost per share, then see how many shares it takes to reach a target average.
Free, no sign-upRuns in your browserHow we calculate
- Total shares
- 150
- Total cost
- $7,000.00
- Break-even price
- $46.6667
How this was calculated
- Total paid = 100 × $50 + 50 × $40 = $7,000.
- Total shares = 100 + 50 = 150.
- Average price = $7,000 ÷ 150 = $46.6667 per share.
Average down (or up) to a target
How this was calculated
- x = owned × (average − target) ÷ (target − price)
- x = 150 × ($46.6667 − $40) ÷ ($40 − $30) = 100 shares
- Cost: 100 × $30 = $3,000; new average ($7,000 + $3,000) ÷ 250 = $40.
Educational, not investment advice. Averaging down lowers your break-even price but adds to a position that is losing money.
How the stock average calculator works
Your average price per share is everything you paid divided by everything you own: average = (shares₁ × price₁ + shares₂ × price₂ + … + fees) ÷ total shares. The stock average calculator adds up each purchase, including commissions, and shows the result as your break-even price: the share price at which the whole position is worth exactly what you put in.
Worked example
You bought 100 shares at $50 and later 50 more at $40. You paid $5,000 + $2,000 = $7,000 for 150 shares, so the average is $7,000 ÷ 150 = $46.67. Note that this is not the simple average of the two prices ($45): the first buy was larger, so it counts for more.
How to average down to a target price
Averaging down means buying more shares after the price falls to pull your average toward it. To reach a target average, solve (owned × average + x × price) ÷ (owned + x) = target for x, which gives x = owned × (average − target) ÷ (target − price). Holding 100 shares at a $50 average with the stock at $30, a $40 average takes 100 × ($50 − $40) ÷ ($40 − $30) = 100 shares, costing $3,000. Check: ($5,000 + $3,000) ÷ 200 = $40. The closer your target is to the current price, the faster the number of shares explodes: a $35 target in the same case needs 300 shares. The target can never reach the current price itself, and the same formula works in reverse for averaging up.
When the average misleads
A lower average only means the stock needs a smaller rebound to get you back to even; it does not make the position less risky, and averaging down puts more money into something that is falling. After a stock split, divide old prices by the split ratio and multiply share counts by it before entering them, or the average will be off. For taxes, the IRS does not use your average for stocks: shares sold come from the oldest lots first unless you choose specific ones; use the cost basis calculator for that.
Sources
IRS Publication 551 (cost basis includes commissions), IRS Publication 550 (identifying shares sold, FIFO and average basis for fund shares), SEC Investor.gov (dollar-cost averaging and stock splits).
Frequently asked questions
How do you calculate the average price of a stock?
Add up what you paid for every purchase, including fees, and divide by the total number of shares. 100 shares at $50 plus 50 at $40 cost $7,000 for 150 shares, an average of $46.67.
How many shares do I need to buy to average down?
Shares = owned × (average − target) ÷ (target − current price). With 100 shares at $50 and the stock at $30, reaching a $40 average takes 100 more shares, or $3,000.
Can I average down below the current price?
No. Every new share pulls the average toward the price you pay, so the average can get close to the current price but never reach or pass it.
Should I include commissions?
Yes. Fees paid to buy are part of your cost, so they raise the average price and the price at which you break even.
Is the average price the same as my cost basis?
It is the average cost basis per share. For taxes on stocks, the IRS uses first in, first out unless you pick specific lots; the average-cost method is allowed only for mutual funds and dividend reinvestment plans.