How do you calculate the average price of a stock?

Divide the total amount you invested by the total number of shares you own. Total invested is the sum of (shares × price) for every purchase. This is a weighted average — for example, 50 shares at $100 plus 150 shares at $40 = $11,000 ÷ 200 shares = $55 average price.

Why is the average not just the midpoint of my buy prices?

Because each price must be weighted by the number of shares bought at it. Buying $100 once and $40 once only averages to $70 if you bought equal share counts. If you bought far more shares at the lower price, your true average is much closer to $40. Ignoring share quantity can make your average off by 20–40%.

Should I include brokerage fees in my average cost?

Yes, for your true cost basis. Add total fees (brokerage, taxes, stamp duty) to your total invested before dividing by shares: (Total Invested + Total Fees) ÷ Total Shares. Fees raise your real break-even, especially with frequent small trades.

Is my average price the same as my break-even price?

Yes, before fees and taxes. Your average cost per share is the price at which you neither gain nor lose. Sell above it for a profit, below it for a loss. Capital-gains tax then applies on top of the cost basis when you sell at a profit.

How does buying more shares change my average price?

Buying below your current average lowers it (averaging down); buying above it raises it (averaging up). How much it moves depends on the size of the new lot relative to your existing holding. A large lot at a much lower price pulls the average down sharply.

How to Calculate Average Stock Price (Formula + Examples)

If you have bought the same stock more than once — at different prices — there is only one number that tells you where you actually stand: your average cost per share. Get it wrong and every profit-and-loss decision you make afterwards is built on a bad foundation. Here is exactly how to calculate it.

Key Takeaways

6 points

1
Average stock price = total amount invested ÷ total shares owned. It is a weighted average, not a simple average of the prices.
2
The simple average of your buy prices is almost always wrong — it ignores how many shares you bought at each price.
3
Add brokerage and transaction fees to your total cost to get your true average cost basis.
4
Your average price is also your break-even price (before fees) — the price you need to sell at to neither gain nor lose.
5
Buying more shares as the price falls (averaging down) lowers your average; buying as it rises raises it.
6
The Stock Averager Calculator does the weighted math for unlimited lots instantly.

The Formula for Average Stock Price

The average price you paid per share is a weighted average — each purchase price is weighted by the number of shares you bought at that price. The formula is simple:

Average Cost Per Share

Average Price = Total Amount Invested ÷ Total Number of Shares

Where Total Amount Invested = (Shares₁ × Price₁) + (Shares₂ × Price₂) + … for every purchase.

Why You Cannot Just Average the Prices

This is the single most common mistake. Say you buy a stock at $100 and later at $50. Most people assume their average is $75 — the midpoint. That is only true if you bought the same number of shares at each price. Buy 10 shares at $100 and 90 shares at $50, and your real average is far closer to $50, because the vast majority of your shares were bought cheaply.

The number of shares at each price is the weight. Ignore it and your average can be off by 20–40%.

Step-by-Step Example (Two Purchases)

Purchase 1: 50 shares at $100 = $5,000 invested.

Purchase 2: 150 shares at $40 = $6,000 invested.

Calculating the weighted average

Total invested = $5,000 + $6,000 = $11,000

Total shares = 50 + 150 = 200

Average price = $11,000 ÷ 200

= $55 per share

Note that the simple average of $100 and $40 is $70 — but your true average is $55, because you bought three times as many shares in the second, cheaper lot. That $15 difference per share is the difference between thinking you are down and knowing you are actually up if the stock trades at $60.

Multiple Purchases (More Than Two Lots)

The formula does not change — you just sum every lot. Here is a four-purchase example:

Purchase	Shares	Price	Amount
Lot 1	100	$80	$8,000
Lot 2	50	$70	$3,500
Lot 3	75	$60	$4,500
Lot 4	25	$50	$1,250
Total	250	—	$17,250

Average price = $17,250 ÷ 250 = $69 per share. With four lots the arithmetic is error-prone by hand — this is exactly where a calculator earns its keep.

Don't Forget Fees: Your True Cost Basis

Your cost basis is what the tax authorities (and reality) care about, and it includes every cost of acquiring the shares — brokerage, exchange fees, stamp duty, and any transaction taxes. To get your true average cost, add total fees to your total invested before dividing:

True Average Cost (with fees)

True Average = (Total Invested + Total Fees) ÷ Total Shares

On the example above, if you paid $50 in total brokerage across the four buys, your true average becomes ($17,250 + $50) ÷ 250 = $69.20. It is small here, but on frequent small trades fees can move your real break-even by a meaningful amount. See our Break-Even Calculator to fold fees and taxes into the exit price you actually need.

Average Price Is Your Break-Even Price

Your average cost per share is also the price at which you break even (before fees). Sell above it and you profit; sell below it and you take a loss. This is why the number matters so much: every "should I sell?" and "am I up or down?" question is measured against your average. If your average is $69 and the stock is at $75, you are up about 8.7% — regardless of what any single purchase price was.

How Averaging Down Changes Your Average

When you buy more shares at a price below your current average, your average falls — this is called averaging down. When you buy above your average (averaging up), it rises. The size of the move depends on how many shares you add relative to what you already hold. Adding a large lot at a much lower price pulls the average down hard; adding a token amount barely moves it.

Knowing your post-purchase average before you commit capital is the whole point — it tells you the new break-even you are signing up for. Read break-even after averaging down for the trade-off between a lower average and more capital at risk.

Calculate It Instantly

Doing weighted averages by hand across many lots invites arithmetic slips. The Stock Averager Calculator takes any number of purchases and returns your exact average cost, total shares, and total invested — and it can also tell you how many shares to buy at the current price to hit a target average. Enter each lot's shares and price, and it handles the math (in any of 10 currencies).

Common Mistakes to Avoid

Averaging the prices instead of weighting by shares — the error that started this article.
Forgetting sold shares — if you have sold part of your position, your average only reflects the lots you still hold (depending on your accounting method: FIFO, LIFO, or average cost).
Ignoring fees — small per-trade costs quietly raise your real break-even.
Confusing average price with break-even after tax — capital-gains tax applies on top of your cost basis when you sell at a profit.
Mixing currencies — if you bought on different exchanges, convert everything to one currency before averaging.

Disclaimer

All examples are for educational illustration only and use simplified numbers. Tax treatment of cost basis varies by country and accounting method. This is not investment or tax advice — consult a licensed professional before making decisions.