Dollar-Cost Averaging Calculator
See how regular fixed investments accumulate shares and what the position is worth.
Dollar-cost averaging means investing the same amount on a schedule, automatically buying more shares when prices dip and fewer when they rise. Enter your periodic investment and a price series to see total shares accumulated, your average cost per share, and the final portfolio value.
How to use this calculator
- Enter the fixed amount you invest each period (e.g. $100 per month).
- Enter one price per period, oldest first — separated by commas, spaces, or newlines.
- Optionally click 'Use example price series' to see how it works with illustrative data.
- Click Calculate to see shares accumulated, average cost, and final value.
The formula
Shares per period = Investment / Price; Average Cost = Total Invested / Total Shares
Worked example
Investing $100 per month for 2 months at prices of $10 then $20 buys 10 + 5 = 15 shares. With $200 invested, the average cost is $13.33 per share, worth $300 at the final $20 price — a $100 (50.00%) gain.
Frequently Asked Questions
What is dollar-cost averaging?
Dollar-cost averaging (DCA) is investing a fixed dollar amount on a regular schedule — say $500 every month — regardless of price. It's the default behavior of 401(k) contributions. The discipline removes timing decisions and emotions from investing.
Why does DCA buy more shares when prices fall?
Because the dollar amount is fixed: $100 buys 10 shares at $10 but only 5 shares at $20. When prices dip, the same money buys more shares, which lowers your average cost per share. That's the mechanical advantage this calculator demonstrates.
Does dollar-cost averaging guarantee a profit?
No. If prices fall and never recover, DCA loses money like any other strategy — it just loses less per share than buying everything at the peak would have. DCA manages timing risk; it doesn't eliminate market risk.
What prices should I enter?
Use real historical prices in chronological order, oldest first — for example, an index fund's monthly closing prices over the period you're modeling. Paste them separated by commas, spaces, or newlines. The example series button fills in clearly-labeled illustrative data, not real market prices.
Is DCA better than investing a lump sum all at once?
Research (notably a Vanguard study) finds lump-sum investing outperforms DCA about two-thirds of the time, because markets rise more often than they fall. But DCA wins on psychology: it keeps nervous investors in the market instead of waiting for a 'perfect' entry that never comes.