What Is Dollar-Cost Averaging?

If you've ever contributed the same amount to an investment from every paycheck, you've already practiced dollar-cost averaging — you just may not have called it that. Here's what the term actually means, how it works mechanically, and how it compares to investing a lump sum all at once.

The definition

Dollar-cost averaging (DCA) means investing a fixed dollar amount on a fixed schedule — weekly, monthly, or whatever cadence you choose — regardless of whether the price is higher or lower than last time. The amount stays the same; the number of shares it buys changes with the price.

How it works, step by step

1. You decide on a fixed amount (say, $500) and a schedule (say, monthly).
2. On each scheduled date, you invest that amount, whatever the current price happens to be.
3. When the price is lower, your fixed amount buys more shares. When it's higher, it buys fewer.
4. You repeat this on the same schedule, without trying to time individual purchases.

A simple illustration

To see the mechanism clearly, here's $100 invested every month for four months at a set of hypothetical prices — not real VOO price history, just round numbers chosen to illustrate how the math works:

Total invested: $400, for a total of about 20.101 shares — an average cost of about $19.90 per share. The simple average of the four prices themselves is exactly $20.00. Because the fixed dollar amount bought more shares when the price dipped to $18, the average cost per share came out slightly below the simple average of the prices. This is the mechanical effect people mean when they describe DCA as "averaging out" your purchase price — it isn't guaranteed to always work out this way, since it depends on the specific price path.

Why people use it

• It matches how most people get paid. Investing from each paycheck is naturally a recurring, fixed-amount pattern.
• It removes a difficult decision. You don't have to decide whether today is a good day to invest a large sum — you just follow the schedule.
• It can reduce regret. Spreading purchases out means no single purchase date determines your entire outcome.

DCA vs. investing a lump sum

If you already have the full amount available, you could instead invest it all at once — a lump sum — rather than spreading it out. Each has a genuine trade-off, and neither is objectively correct for everyone:

• A lump sum spends more time invested on average, since none of the money sits on the sidelines waiting for a later purchase date.
• DCA spreads the risk of a single bad-timing decision across multiple purchase dates, which can matter more for how comfortable you feel with the decision than for the math itself.
• You can also combine both — invest an initial amount as a lump sum, then continue with regular contributions afterward.

How this connects to investing in VOO

Most people who invest in VOO through a monthly contribution — from a paycheck, a brokerage auto-invest feature, or a retirement account — are already dollar-cost averaging, whether or not they use the term. Our VOO Investment Calculator lets you model an initial lump sum, an ongoing monthly contribution, or both together, so you can compare how each pattern plays out under the same return assumption.