Dollar-Cost Averaging Calculator
Steady investing, measured honestly.
Compare investing a fixed amount every month with investing the same total on day one. Pick a price pattern and see average cost, shares bought and the ending value of each approach.
- Free, no sign-up
- Runs in your browser
- Shareable results
- Educational only
Set up the comparison.
One purchase at the start of every month.
Whole years, from 1 to 30.
The price at the first purchase.
The long-run drift in price.
Prices wander around the trend in this shape.
The price paths are illustrative patterns, not forecasts. These are hypothetical assumptions for learning, not forecasts or expected results for any investment.
Result
Steady purchases versus one lump sum.
View the year-by-year table
What the numbers mean.
Average cost sits below average price.
When you invest a fixed amount, you automatically buy more shares when prices are low and fewer when they are high. The average cost per share is therefore always at or below the simple average price.
It is a habit, not a guarantee.
Dollar-cost averaging does not remove the risk of loss. Over a rising market a lump sum often wins, because more money is invested for longer. The monthly plan reduces the risk of a badly timed single purchase.
The path matters most.
Change the price pattern and the winner can switch. That is the point: nobody knows the path in advance, so the calculator shows how each approach behaves.
About this dollar cost averaging calculator.
A dollar-cost averaging calculator shows what happens when you invest the same amount at regular intervals instead of all at once. Enter your monthly amount, the number of years, a starting share price and a price pattern. The calculator then compares the monthly plan with a lump sum of the same total, using your average cost per share, the shares bought and the ending value.
Dollar-cost averaging, often shortened to DCA, spreads purchases over time so you buy more shares when prices are low and fewer when they are high. Read our dollar-cost averaging guide for the full idea, or see how regular investing fits into building an ETF portfolio. The glossary definition of dollar-cost averaging is a quick refresher.
How the dollar cost averaging calculator works in practice.
Say you invest $500 a month for 5 years, which is 60 purchases and $30,000 in total. The share starts at $100, the underlying trend is 7% a year, and the price dips before it recovers.
Average cost per share: $94.01
Average market price: $95.99 (2.06% above your average cost)
Ending value, monthly plan: $44,760
Ending value, $30,000 lump sum on day one: $42,077
Monthly plan minus lump sum: $2,683
In this dip-then-recovery pattern the monthly plan finished ahead because it bought more shares at the lower prices. Change the pattern to “Steady market” and the lump sum wins by $6,277, because money invested earlier had longer to grow. The pattern matters more than the method, which is why the calculator lets you test several.
How to choose your inputs.
Amount invested each month. The sum you can invest on a schedule without touching it. The calculator compares it with the same total invested at the start.
Years of investing. Longer periods give prices more time to move, so the gap between the two methods can grow.
Starting price per share. Only the pattern of price changes matters, so any starting price works. Use a real price if you want share counts that match a fund you follow.
Underlying yearly price trend. The long-run direction of the price, as a yearly percentage. Try a low figure, a high figure and a negative one.
Price pattern. Choose a dip, a steady market, a rise then fall, or a volatile ride. Real prices follow none of these exactly.
How the dollar-cost averaging calculator works.
The model builds a price for every month from a steady yearly trend and the pattern you choose. The monthly plan buys amt ÷ price shares at the start of each month. The lump sum buys the whole total at the first month’s price.
Shares bought in a month = monthly amount ÷ price(t)
Average cost = total invested ÷ total shares
Average market price = simple average of the monthly prices
Money waiting to be invested earns nothing in this model, and fees, taxes and dividends are excluded. Real prices are noisier than these smooth patterns.
Limits of this dollar cost averaging calculator.
Real prices do not follow a fixed pattern, so no scenario shown here predicts what will happen. The model ignores trading fees, taxes, dividends and the interest a lump sum waiting to be invested could earn. In a market that mostly rises, investing earlier tends to do better than spreading purchases, while in a falling or recovering market spreading them can help. Many people invest monthly because it matches how they are paid, not because it beats the alternatives.
Common questions about the dollar cost averaging calculator.
Is dollar-cost averaging better than a lump sum?
Neither is always better. A lump sum has tended to do better when markets rise over the period, while regular investing can feel safer and lowers the risk of a poorly timed single purchase. The calculator lets you test both.
Why is my average cost lower than the average price?
Because you buy more shares when the price is low. Mathematically, a fixed-amount plan buys at the harmonic mean of prices, which cannot exceed the simple average.
Does this predict real markets?
No. The price patterns are illustrations. Use them to understand the mechanism, not to forecast.
What if I invest weekly or every paycheque?
The logic is the same. Monthly is used here for simplicity.
How do I calculate average cost per share with DCA?
Divide the total amount invested by the total number of shares bought. With equal monthly amounts, the result is lower than or equal to the simple average of the prices.
Does dollar-cost averaging reduce risk?
It spreads your purchase prices, which can soften the effect of buying at a peak. It does not remove market risk or protect against losses.
How often should I invest?
Monthly is common because it matches pay cycles. Weekly or quarterly schedules would give a similar picture but are not modelled here.
More calculators.
Educational illustration only, not a forecast or personal investment recommendation. Prices follow assumed patterns. The model excludes fees, taxes, dividends and interest on uninvested cash.
Further learning: Dollar-cost averaging explained · How to build an ETF portfolio · Glossary: Dollar-cost averaging · Investor.gov: Financial tools and calculators · Research methodology · Financial disclaimer