Stock Average Calculator
Buying 100 shares at $50 and 150 more at $28 gives a $36.80 average cost across 250 shares — enter your purchases below.
Math illustration only — not financial advice. Averaging down adds money to a falling stock and increases risk; this tool does not recommend buying or selling.
How this stock average down calculator works
Your average cost is a weighted average: every lot counts in proportion to its size, computed as the sum of (shares × price) for all lots divided by total shares. The calculator above applies that formula to each purchase you enter and shows your breakeven price instantly.
Breakeven equals your average cost before fees. If the stock climbs back to your average, your position is whole again — minus whatever you paid in commissions.
The averaging-down planner, explained
The planner answers one question: how many shares at the lower price pull my average down to my target? The answer is shares × (current average − target) ÷ (target − buy price), rounded up to a whole share.
The target must sit between the buy price and your current average. If it does not, the math has no meaningful answer — the tool says so instead of showing a number.
What an average calculator for shares leaves out
Commissions and fees are not included unless you fold them into each lot's price. Dividends do not change your average cost. A stock split changes your share count — adjust the lots before calculating.
Average price = Σ(shares × price) ÷ Σshares · Shares to buy = shares × (avg − target) ÷ (target − buy price)
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Stock average calculator FAQ
What is averaging down in stocks?
Averaging down means buying more shares of a stock you already own at a lower price, which pulls your average cost per share down. Example: owning 100 shares at $50 and buying 100 more at $30 moves your average from $50 to $40.
What is the stock average formula?
Average cost per share = (shares₁ × price₁ + shares₂ × price₂ + …) ÷ total shares. Each lot is weighted by its size, so a bigger purchase moves the average more than a small one.
Is the breakeven price the same as average cost?
Yes, before fees and commissions: you break even when the stock price returns to your average cost per share. Brokerage commissions and fees push the true breakeven slightly higher.
Can you show a worked example with three different buy prices?
Buy 50 shares at $40 ($2,000), 75 shares at $32 ($2,400), and 25 shares at $48 ($1,200). Total invested is $5,600 across 150 shares, so the average cost is $5,600 ÷ 150 = $37.33 per share.
Does averaging down always work?
No. Averaging down always lowers your breakeven price, but it also concentrates more money in a stock that is falling. Whether that is wise depends on the company and your own judgment, not on the math. This calculator shows the arithmetic only and is not financial advice.