Type the amount you put in each period and the price you paid that period. The page works out the shares each period bought, then your total invested, your total shares and your average cost per share — the figure people mean when they ask what their average is after dollar-cost averaging. A dollar cost averaging calculator is asking for the same sum, one period on each row, and this page answers it at the bottom. The arithmetic is printed underneath, using your own numbers.
Each period
Amount investedPrice per shareShares bought
Current price per share — optionalNo live price feed here — type the price yourself, or leave this empty to get your cost and average only.
Average cost per share—
Total shares—
Total invested—
Market value—
Profit / loss—
Return—
How your average cost is worked out
Regular investing means the same amount of money goes in period after period, so the number of shares you get changes with the price: a cheap period buys more shares, an expensive period buys fewer. The page works each period out on its own, then averages the lot.
Shares bought in a period = amount invested that period ÷ price per share that period
Total invested = amount1 + amount2 + …
Total shares = shares1 + shares2 + …
Average cost per share = total invested ÷ total shares
Market value = total shares × current price
Profit / loss = market value − total invested
Return = (profit / loss ÷ total invested) × 100
Average cost per share = (a1 + a2 + … + an) ÷ (a1÷p1 + a2÷p2 + … + an÷pn)
where a is the amount put in that period and p is the price per share paid in that period. The top of that fraction is the money in; the bottom is everything those periods bought. It is the same weighted average used everywhere on this site — the shares are what do the weighting, and they come out of the division above.
Worked example: three periods of 1,000 each, at 50, 60 and 45. The shares are 1,000÷50 = 20.0000, 1,000÷60 = 16.6666 and 1,000÷45 = 22.2222, so 58.8888 shares for 3,000.00 invested, and an average cost of 3,000.00 ÷ 58.8888 = 50.9434. Type those three rows in and the page returns that figure.
Notice it is below the plain average of the three prices (51.6666). The cheap third period bought more shares than the dear second one, so it pulls the average down harder than the second period pulls it up. That is the whole point of the weighting, and it is why a plain average of your prices is the wrong number.
Three periods of 1,000.00 at three different prices. The cheap period buys the most shares, so it weighs the most, and the average lands below the plain average of the three prices.
Rounding: every figure on this page is rounded down, never up — the same rule as the rest of the site. Share counts and prices are shown to four decimals and amounts to two, so the number you read is never larger than the one that was computed. Share counts keep all four decimals even when they come out whole, so every period lines up with the total. The total shares is the sum of the per-period figures exactly as they are printed beside each row, so the column and the total agree with each other.
Equal amounts are what make the average fall
The statement that regular investing gives you a lower average cost than the plain average of the prices is true for one specific reason: the same amount of money goes in every period. It is not a property of averaging by itself. If the amounts change, the same arithmetic can put your average cost above the plain average of the prices instead.
Keep the three prices fixed at 10.00, 20.00 and 30.00, and keep the total fixed at 3,000.00. The plain average of the three prices is 20. Change only where the money goes. The arithmetic on this page gives these five answers:
Amounts at 10.00 / 20.00 / 30.00
Total shares
Average cost
Where it lands
1,000 / 1,000 / 1,000 (equal)
183.3333
16.3636
below 20
100 / 100 / 2,800
108.3333
27.6923
above 20
2,800 / 100 / 100
288.3333
10.4046
below 20
2,998 / 1 / 1
299.8833
10.0038
below 20
1 / 1 / 2,998
100.0833
29.975
above 20
The same three prices and the same 3,000.00 in. Only the split of the money changes, and the average cost moves from 10.0038 to 29.975 across that one change.
The first row is the textbook case: 1,000.00 in each period, and the average cost comes out at 16.3636. With equal money going in, that figure is the harmonic mean of the three prices. It sits below 20 because at 10.00 the fixed amount buys 100.0000 shares, at 20.00 it buys 50.0000 and at 30.00 it buys 33.3333, so the cheap periods hold most of the shares. Equal amounts are the condition that makes that true.
Take the condition away and the guarantee goes with it. In the second row 2,800.00 goes in at 30.00 and only 100.00 at each of the cheaper prices. The total is still 3,000.00 and the prices are still the same three, but the average cost is 27.6923, above the plain average of 20. Most of the money bought the dearest shares, and the weighting follows the money, not the number of periods. The third row is the mirror of it: put 2,800.00 into the cheapest period instead and the average falls to 10.4046, below even the equal-amount row.
The last two rows show the limits. With 2,998.00 of the 3,000.00 in the 10.00 period the average is 10.0038, almost exactly the cheapest price. With 2,998.00 in the 30.00 period it is 29.975, almost exactly the dearest. All five answers sit between 10.00 and 30.00, which is where any average of these three prices has to sit; what moves is where in that range the money puts you. So the statement to keep is not that regular investing lowers your average cost. It is that equal amounts do, and unequal amounts can do the opposite.
This page takes no position on which of those five schedules is better. Type the amounts you actually put in, period by period, and it returns the one average cost that belongs to them. The comparison above is arithmetic on the same three prices, not a recommendation.
What is counted, and what is not
This page uses only the amounts and the prices per share you type in. Nothing else goes into the arithmetic.
Not counted: anything outside the amounts and the prices per share you type. Broker charges, tax, dividends, splits and other corporate actions, a part-sale of the holding and currency conversion all sit outside the arithmetic, and no box on this page asks for them.
No live prices. This page never fetches a quote and has no connection to a market data source, so it can never show you a price that is not real. Every price on the page — each period's, and the current one — is yours to type.
Not built: several tickers at once, saving your history, signing in, or placing an order. There is no account here and nothing is stored.
Fractional shares are counted in full. 1,000 at 60 gives 16.6666 shares, not 16. If your broker only handles whole shares, your own figure will differ from this one.
If you want a commission to show up in the average, subtract it from that period's amount before typing it in — the shares come out slightly lower and the average slightly higher. Left as it is, the result is a before-fee figure. Amounts are shown in whatever currency you typed; no exchange rate is applied anywhere.
The result is the average cost of the periods you entered. It is not a view on whether that schedule suits you, and this page takes no position on it.
Frequently asked questions
What are the downsides of dollar-cost averaging?
This page is a calculator, so it will not tell you whether a schedule suits you. There is one arithmetic downside worth naming, though: a lower average cost is not automatic. It comes from putting the same amount in each period. If most of the money goes in when the price is high, the average cost of the periods you entered can come out above the plain average of those prices, not below it. On 10.00, 20.00 and 30.00 with 3,000.00 split unequally, the average ranges from 10.0038 to 29.975 depending only on where the money went. Type your own amounts period by period and the page returns the average that belongs to them, without assuming anything about the strategy.
How do I calculate dollar cost average over the periods I have already invested?
Put one period on each row — the amount that went in and the price per share that period — and the page does the rest: each amount is divided by its own price to get the shares that period bought, the money is added up, the shares are added up, and the money is divided by the shares. That last division is the average cost, and it is printed line by line under the results. Nothing else needs typing.
Is a DCA calculator the same thing as a dollar cost averaging calculator?
Yes — DCA is short for dollar-cost averaging, and both names ask for the same arithmetic: money in per period, price per period, and the average cost that comes out. This is one page, not two.
I have seen this called a dca calculator stock and a stock dca calculator — same thing?
Same page, under two other word orders. A dca calculator stock and a stock dca calculator both describe this one: a set amount going in period after period, the price paid each period, and the average cost per share those periods came to. Which of the three you searched for makes no difference to what is worked out here.
What does a DCA calculator work out, exactly?
Three things from the figures you type: the shares each period bought, your totals (money in and shares held), and your average cost per share. If you also type a current price, it adds market value, profit or loss and return. That is the whole page.
Do I enter the amount I invested, or the number of shares I bought?
The amount. That is what regular investing fixes in advance — the money — while the number of shares follows from the price. The page divides for you and prints the shares next to each row. If you already know the share counts and want the average of those purchases instead, use the stock average calculator on the home page, which takes shares directly.
Can it look up the price I paid, or the price now?
No. There is no price lookup on this page and no connection to any market data source, by design — a fetched price can be wrong, delayed, or for the wrong ticker, and this page would rather show nothing than show a number it did not get from you. Type the prices yourself.
Does it count fees, commissions or taxes?
No. There is no field for any of them, so the average you get back is before those costs. To see one period with a commission in it, subtract the commission from that period's amount before typing it in; the shares come out lower and the average higher. Taxes on a sale are outside this page entirely — it averages what you bought, not what you owe.
How many periods can I enter?
As many as you need. The page starts with two periods — one period on its own just returns the price you typed — then use + Add period for each extra one and the × on a row to remove it. There is no cap.
How is this different from the other calculator in this site's menu?
The home page takes the share counts you already own and averages them. This page takes the money you put in each period and works the share counts out first, which is the regular-investing way round. The average both pages return is the same weighted average; only the inputs differ. If you are working out what a further purchase would do to an average you already have, use the average down calculator.
Does this page tell me whether I should keep investing on a schedule?
No, and nothing here should be read that way. The page does the arithmetic on the periods you enter; it does not compare approaches, rank them, or tell you what to do with your money. It answers one question only: given these amounts and these prices, what is my average cost per share?
Does it work on my phone, and do I need an account?
Yes to the first, and no to the second. The fields stack to a single column on a narrow screen and the results stay inside the width of the page. There is no sign-up, no pop-up and nothing to install: the whole calculation runs in your browser, and your numbers are not sent anywhere.
This page is a calculator, not investment advice. A lower average cost does not make a position safer. Contact: contact@stockavg.com