Stock Average Calculator
Find your average cost per share across multiple buys
🧮 Your buys
Fees & current price (optional)
Last updated June 2026
Method: Weighted-average cost - total dollars paid (optionally including commissions) divided by total shares. Break-even equals the resulting average cost per share.
Included: Unlimited buy lots, total shares, total invested, average cost per share, per-buy weighting, break-even price, and unrealized gain or loss at a price you enter.
Not included: Dividends (unless you add reinvestments as buys), automatic stock-split adjustments, wash-sale rules, and alternative tax-lot methods such as FIFO or specific identification.
Stock average calculator: everything you need to know
Say you bought 100 shares at $50, then 50 shares at $40, and later 25 shares at $30. People often guess their average is the middle of those prices - about $40 - but that ignores how many shares you bought at each price. The real math is total cost divided by total shares: ($5,000 + $2,000 + $750) ÷ 175 shares = $44.29 per share. That weighted figure is your true cost basis, and it is exactly what this stock average calculator computes for any number of buys.
The formula
The average cost per share is a weighted average of every purchase:
Average cost = Total cost ÷ Total shares where Total cost is the sum of (shares × price) for every buy, plus any commissions, and Total shares is the sum of all shares purchased. Because it weights each price by the number of shares, a large buy moves your average far more than a small one. The result is also your break-even price - the price you must sell at just to get your money back.
How to use this calculator
You only need the size and price of each purchase. Work through the fields in order:
- Enter your first buy: type the number of shares and the price you paid per share.
- Add more buys: tap "Add another buy" for each additional purchase - there is no limit, so you can capture every lot.
- Commissions (optional): if you paid a trading fee per order, add it so the cost basis and break-even reflect it.
- Current price (optional): enter today's market price to see your position's value and unrealized gain or loss.
- Calculate: read your average cost per share, total shares, total invested, and break-even, plus a buy-by-buy table.
Use the breakdown table to see how much each purchase contributes to your blended cost - that weight is why a big position dominates the average.
Who this calculator is for
This tool helps anyone who has bought the same asset more than once and wants a single, accurate cost number:
- Dollar-cost-averaging investors who buy on a schedule and want their blended cost.
- Dip buyers deciding whether and how much to average down on a falling stock.
- Long-term holders reconstructing a cost basis across years of purchases.
- DRIP participants who reinvest dividends and need to fold each reinvestment into the average.
- ETF, mutual fund, and crypto buyers - the math is identical for any asset bought in lots.
Key terms explained
- Cost basis: the total amount you paid for your shares, including commissions. Dividing it by share count gives your average cost.
- Average cost per share: your weighted-average purchase price - the headline result of this calculator.
- Break-even price: the price at which you neither gain nor lose; for a buy-and-hold position it equals the average cost.
- Averaging down / up: buying more below (down) or above (up) your current average, which lowers or raises your blended cost.
- Unrealized gain/loss: the paper profit or loss based on the current price; it becomes "realized" only when you sell.
- Tax lot: a group of shares bought together. Brokers track lots so you can choose which to sell (FIFO, specific ID, or average cost).
Worked example: averaging down
You bought 200 shares at $60 ($12,000), and the stock has fallen to $40. Your average is $60 and you are down $4,000 on paper. If you buy another 200 shares at $40 ($8,000), your totals become $20,000 across 400 shares - a new average of $50 per share. Your break-even drops from $60 to $50, so the stock only needs to recover to $50 (not $60) for you to be whole. The trade-off: you now have $20,000 at risk instead of $12,000, so a further drop hurts more in dollar terms.
Worked example: dollar-cost averaging
Instead of timing the market, you invest $500 every month regardless of price. In a choppy market you might buy 10 shares at $50, then 12.5 shares at $40, then 8.3 shares at $60. Because $500 buys more shares when the price is low and fewer when it is high, your average cost ends up below the simple average of the prices. Entering each monthly purchase here shows the blended cost that disciplined, automatic buying produces over time.
Worked example: with commissions
Suppose you made three buys of 100 shares at $20, $25, and $30, and your broker charges a $7 commission per order. The shares cost $7,500 and commissions add $21, for a total of $7,521 across 300 shares - an average of $25.07 rather than the $25.00 you would get ignoring fees. Commissions are small at most modern brokers, but on small positions or fee-charging products they nudge your break-even higher, which is why the calculator can fold them in.
What changes the result the most
As you adjust the inputs, a few factors dominate the average:
- Share quantity per buy: the average is weighted by shares, so your largest purchase pulls the result toward its price.
- Price spread between buys: the wider the gap between your highest and lowest purchase prices, the more averaging moves the number.
- Order of buys does not matter: only totals count - rearranging the same purchases gives the same average.
- Commissions: small on big positions, but meaningful on tiny ones or fee-charging products.
- Reinvested dividends: each one is effectively a new buy and gradually shifts the average.
Tips for using your average cost
- Decide before you average down. Set a rule for how much you will add and at what price, rather than buying emotionally on every dip.
- Watch position size. A lower average is no comfort if one stock becomes an outsized share of your portfolio.
- Track the break-even, not the entry. The price you first paid is history; your blended break-even is the number that matters now.
- Mind your tax method. If you might sell only part of a position, FIFO or specific-lot selling can change your taxable gain versus the average.
- Re-run after every buy. Add each new purchase so your average and break-even stay current.
Limitations and assumptions
This calculator is a planning estimate, not tax or investment advice. Keep these assumptions in mind:
- It uses the weighted-average method; your broker may report a different cost basis under FIFO or specific identification.
- It does not auto-adjust for stock splits - enter post-split share counts and prices if a split occurred.
- It ignores wash-sale rules, which can disallow a loss if you rebuy the same security within 30 days.
- Cash dividends are not included unless you add each reinvestment as a separate buy.
- The unrealized gain or loss uses the single current price you type and does not include taxes on a sale.
How it compares to related calculators
This page answers "what did my shares cost me on average?" If your question is different, a sister tool fits better:
- To measure the percentage return on a position, use the ROI Calculator.
- To project growth from regular contributions and a return rate, use the Investment Calculator.
- To see how reinvested earnings snowball over time, use the Compound Interest Calculator.
- To plan retirement accounts, use the 401(k) Calculator or Roth IRA Calculator.
Sources
- U.S. Securities and Exchange Commission (SEC), Investor.gov - Cost Basis.
- U.S. Securities and Exchange Commission (SEC), Investor.gov - Stocks.
- Internal Revenue Service (IRS) - Topic No. 409, Capital Gains and Losses.
- Internal Revenue Service (IRS) - Publication 550, Investment Income and Expenses (cost basis and wash sales).
⚠️ Common mistakes & edge cases
Averaging the prices instead of weighting by shares
The average of $50, $40, and $30 is $40 - but if you bought far more shares at $50, your real average is higher. Always weight by the number of shares in each buy, which this calculator does automatically.
Forgetting to update after a stock split
A 2-for-1 split doubles your shares and halves the per-share price. If you enter old pre-split prices with new share counts (or vice versa), the average will be wrong. Use post-split figures consistently.
Assuming a lower average means lower risk
Averaging down cuts your break-even but adds money to a falling position. If the decline is fundamental rather than temporary, you can lose far more in dollars than you would have by not adding.
Confusing average cost with your tax cost basis
If you sell only some shares, your broker may use FIFO or specific lots, not the simple average. The taxable gain can differ from what this weighted-average figure suggests - check your broker's accounting method.
❓ Frequently asked questions
How do you calculate the average price of a stock?
Add up the total amount you paid across every purchase (shares times price for each buy), then divide by the total number of shares you own. The formula is: average cost per share = total cost / total shares. For example, 100 shares at $50 plus 50 shares at $40 is $5,000 + $2,000 = $7,000 across 150 shares, or $46.67 per share.
What is averaging down?
Averaging down means buying more of a stock you already own at a lower price than you paid before, which pulls your average cost per share down. If your average was $50 and you buy more at $30, your new blended average falls somewhere between the two, weighted by how many shares you buy at each price. It lowers your break-even but also increases the dollars you have at risk in one position.
What is the break-even price?
The break-even price is the price at which you would recover exactly what you paid, with no profit or loss. For a simple buy-and-hold position it equals your average cost per share. If you include commissions, the break-even rises slightly because those fees are part of your total cost. Selling above break-even is a gain; selling below it is a loss.
Does averaging down always reduce risk?
No. Averaging down lowers your average cost per share, but it also puts more money into a single declining position, which concentrates risk. If the stock keeps falling, you lose more in absolute dollars than if you had not added. Averaging down works when the drop is temporary and the company is still sound - it can be costly when the decline reflects a real deterioration in the business.
Is the average cost the same as my tax cost basis?
Often, but not always. Brokerages let you choose how to account for shares when you sell - average cost, first-in-first-out (FIFO), or specific identification. This calculator uses the weighted average method. If you sell only some shares using FIFO or specific lots, your reported cost basis and taxable gain can differ from the simple average shown here. Check your broker's settings or a tax professional.
How do commissions affect my average cost?
Trading commissions are part of what you paid, so they belong in your cost basis. Adding a fee to each buy raises your total invested and therefore your average cost per share and break-even price. Most major U.S. brokers now charge $0 commission on stock trades, but fees still apply to some products, so the calculator lets you include a per-buy commission if relevant.
What happens to my average cost after a stock split?
A stock split changes your share count and per-share price proportionally but not your total cost basis. In a 2-for-1 split, your shares double and your average cost per share is halved, so the position value is unchanged. This calculator does not auto-adjust for splits - if a split happened, enter your post-split share counts and prices so the average reflects your real position.
Should I include dividends in the average cost?
Cash dividends do not change your cost basis. However, if you reinvest dividends (a DRIP), each reinvestment is effectively a new purchase of shares at that day's price - so you should add it as another buy in the calculator. Reinvested dividends gradually shift your average cost toward the prices at which the dividends bought shares.
Can I use this for crypto, ETFs, or mutual funds?
Yes. The math - total cost divided by total shares or units - is identical for any asset bought in multiple lots, including ETFs, mutual funds, and cryptocurrency. Just enter each purchase as a separate buy with the number of units and the price you paid. Note that mutual funds and crypto may have their own tax-lot rules at your provider.
How is average cost different from market price?
Your average cost is what you paid; the market price is what the asset is worth right now. The gap between them is your unrealized gain or loss. If the current price is above your average cost you are in profit; below it, at a loss - until you actually sell, at which point the gain or loss becomes realized.
💡 Good to know
Order of your buys never changes the average
Because the average is just total cost divided by total shares, it does not matter whether you bought the cheap shares first or last. Only the totals count - so you can enter your lots in any order.
Reinvested dividends are extra buys
If you run a DRIP, each reinvestment purchases shares at that day's price. Add those as additional buys here so your average cost and break-even reflect them, otherwise the figure will be too low.
Your break-even is the number to watch
The price you first paid is history. Once you have multiple buys, the blended break-even is what determines whether selling locks in a gain or a loss - track it, not your original entry.
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