Dollar-Cost Averaging Calculator
The average price you really paid when you buy the same amount at regular intervals.
Good to know. The same amount each month buys more when prices are low, so the average cost lands below the average price.
Not financial advice. Uses only the numbers and rates you enter — no live data.
How it works
In plain words
Each purchase buys the amount divided by that day’s price. Add up the units, then divide the total invested by the units for the average cost. It always comes out at or below the plain average of the prices.
The formula
units = Σ amount ÷ priceᵢ average cost = (amount × purchases) ÷ units worth now = units × price now
Worked example
100 at prices of 50, 40, 25, 40 and 50 buys 2 + 2.5 + 4 + 2.5 + 2 = 13 units for 500, an average cost of 38.46, while the prices averaged 41. At 50 they are worth 650.
Sources
- Investor.gov (US SEC), Dollar cost averaging Investing equal amounts at regular intervals buys more when prices are low and less when they are high.
Sources checked October 3, 2026. 4 automated tests check its answers on every change.
About the dollar-cost averaging calculator
Dollar-cost averaging means investing the same amount at regular intervals, every month for example, whatever the price. Most people do it without choosing to, through a pension or a monthly savings plan.
Because the amount is fixed, each purchase buys more units when the price is low and fewer when it is high. That pulls the average cost per unit below the plain average of the prices: in the example the prices averaged 41, but the units cost 38.46 on average. Mathematically it is the harmonic mean of the prices, which is never above the ordinary mean.
It is not magic. If the price only rises, buying everything on the first day would have done better, and over long periods markets have more often risen than fallen. What regular buying does well is take away the need to pick a moment, smooth out a bumpy ride and turn saving into a habit.
Enter the price at each purchase, oldest first, and the price now; fees are not included. For growth at a steady rate, use the compound interest calculator; for a single purchase, the stock or crypto profit calculator.
Questions people ask
How do I calculate my average cost per share?
Divide the total amount invested by the total number of units bought. 500 invested for 13 units is 38.46 a unit.
Why is my average cost lower than the average price?
Because a fixed amount buys more units when the price is low. Those cheap units weigh more in the average.
Is dollar-cost averaging better than investing all at once?
Not always. In a rising market a lump sum usually does better; regular investing spreads the risk of buying at a peak.