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DCA Calculator
Steady monthly buying or one lump sum — which ends up ahead? This DCA calculator shows the ending value, average cost per share and total return of investing a fixed amount every period, then runs the same money as a lump sum for comparison.
See how this works on $500 a month for ten years — 3 real examples
Ending value after 10 years of dollar-cost averaging
$0
Total invested
$0
Shares accumulated
0
Average cost / share
$0
Total return
0%
DCA vs lump sum
Same $0 put to work two ways: spread across every period, or invested all at once at the starting price.
Return 0%
Return 0%
Share price and your purchases
Year-by-year purchase scheduleHow shares and value build up
| Year | Invested | Avg buy price | Shares held | Value |
|---|
How your dollar-cost-averaging results are worked out
At each purchase you spend the same fixed amount, so the shares you get depend on that period’s price:
sharest = contribution ÷ pricet · average cost = total invested ÷ total shares
Your total shares are the sum of every period’s sharest, the ending value is total shares × final price, and the average cost per share is simply what you paid divided by what you own. The lump-sum comparison takes the exact same total dollars, buys at the very first price, and values those shares at the same ending price.
Because you can’t enter tomorrow’s prices, the calculator synthesizes a price path from your inputs. The trend follows your expected annual return geometrically, pricet = price0 · (1 + r)t/periods per year, and the volatility swing adds a yearly wave around that trend (× (1 + vol · sin(2π · year))). Set volatility to 0 and you get the pure trend. This is a smooth illustration, not a forecast — real markets are random and jagged, so use the ending value as a what-if for comparing plans, not as a prediction. In this deterministic smooth model a lump sum will beat DCA whenever the trend is positive, because it simply spends more time in the market; historically, across real market histories, lump sum still wins roughly two-thirds of the time for the same reason.
The same $500 a month, three markets
Ten years of $500 monthly buys — $60,000 in — dropped into a rising, a falling and a sideways market, each against a day-one lump sum.
A market climbing 8% a year
ending value$84,106
- Steady buying turns $60,000 into $84,106, a 40.18% gain over the decade.
- The same $60,000 invested on day one grows to $119,054 — $34,948 further ahead.
- Waiting to buy costs money in a climb: the average share cost $141.55, not the $100 start.
When the trend is up, every month on the sidelines is the expensive part of averaging in.
Load this example (opens in a new tab)A market sliding 5% a year
ending value$44,062
- Each $500 buys more shares as prices sink, pulling the average cost down to $75.74.
- The slide still hurts — $60,000 shrinks to $44,062, a 26.56% loss.
- A day-one lump sum fares worse at $33,372, leaving the monthly buyer $10,690 ahead.
Averaging in cannot rescue a falling market, but it cushions the landing by thousands.
Load this example (opens in a new tab)A decade of 30% swings, no trend
ending value$53,463
- The price drifts nowhere for ten years, swinging 30% around $100 and finishing at $85.
- Dip-buying drops the average cost to $95.39 a share, under the $100 starting price.
- That edge leaves the monthly buyer at $53,463 — $2,463 ahead of the lump sum’s $51,000.
Choppy-but-flat is where buying the dips does its best work against a lump sum.
Load this example (opens in a new tab)Illustrations only, not financial advice. Your own rate, taxes and insurance will differ — check with a qualified financial advisor before acting on any of this.
Dollar-cost averaging vs lump sum, in plain English
- DCA buys more when it’s cheap. A fixed dollar amount automatically scoops up extra shares during dips and fewer at peaks, which pulls your average cost per share below the simple average of the prices you paid.
- Lump sum usually wins on paper. Because markets trend up, putting the whole amount to work on day one has beaten spreading it out about two-thirds of the time — mostly because it earns returns for longer.
- DCA’s real payoff is lower timing risk. It removes the gut-wrenching decision of investing a large sum right before a possible drop, and it can come out ahead when the market falls early or trades sideways.
- Consistency beats the calendar. Weekly, biweekly or monthly barely changes the outcome; automating the habit so you never skip a purchase matters far more than the exact interval.
- Most people DCA by default. Every paycheck contribution to a 401(k) or brokerage is dollar-cost averaging — you rarely have a lump sum sitting idle to deploy in the first place.
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Frequently asked questions
What is dollar-cost averaging?
Dollar-cost averaging (DCA) means investing a fixed dollar amount at regular intervals — say $500 every month — no matter what the price is doing. Because the amount is fixed, you automatically buy more shares when prices are low and fewer when prices are high, which smooths out your entry price over time.
How is average cost per share calculated?
Divide the total amount you invested by the total number of shares you bought across every purchase. This DCA calculator does exactly that: if you put in $6,000 and accumulated 50 shares, your average cost per share is $120. It is a blended cost basis, not the simple average of the prices you paid.
Is dollar-cost averaging better than lump sum?
Historically, investing a lump sum all at once has beaten dollar-cost averaging about two-thirds of the time, because markets trend upward and a lump sum puts every dollar to work sooner. DCA wins more often when the market falls early or chops sideways. Its real value is reducing timing risk and the stress of investing a large sum right before a drop.
Does DCA guarantee a profit?
No. Dollar-cost averaging lowers your average cost in volatile or declining markets and removes the temptation to time the market, but it cannot protect you from a sustained downtrend. If the asset keeps falling, spreading your buys out simply means you lose money more slowly than a lump sum would.
How often should I invest with DCA?
The most common intervals are weekly, biweekly, or monthly, and many investors align their purchases with each paycheck so the habit runs on autopilot. The interval matters far less than staying consistent — this calculator lets you compare weekly, biweekly, monthly, and quarterly schedules to see how little the ending value changes.
How does this DCA calculator model future prices?
Since nobody knows tomorrow’s prices, the tool builds a price path from your starting price and an expected annual return, then adds an optional volatility swing so you can see how choppiness affects your average cost. It is an illustration, not a forecast — real markets are far more random, so treat the ending value as a what-if, not a promise.
Disclaimer: these calculators are educational tools, not financial advice. They model your inputs with published formulas, but they cannot know your full situation — for decisions with real stakes, talk to a qualified professional. Formulas and defaults last reviewed .