DCA (Dollar-Cost Average) Calculator

How it works

What this calculator does

Dollar-cost averaging means investing a fixed dollar amount at regular intervals regardless of price. This tool takes each contribution and the price it bought at, then returns the total units accumulated and your average cost per unit across the whole plan.

The formula

It uses a dollars-in model — you enter money spent, not share counts:

units = Σ (amount / price)

average cost = Σ amount / Σ units

Because a fixed amount buys more units when prices are low, the average naturally tilts below the simple mean of the prices.

Worked example

You invest $300 three times: at $30, $20 and $15. Units bought are 10 + 15 + 20 = 45 for $900 total, so your average cost is 900 / 45 = $20.00 — lower than the $21.67 simple average of the three prices, because more units were bought cheaply.

What it deliberately does not do

It does not forecast returns or claim DCA beats a lump sum; that depends on the path of prices. The order in which the prices occur doesn't change the average — only the amounts invested and the prices paid do. It uses the figures you enter, not live quotes, and it is for education, not investment advice.