How Regular Investing Works, What It Can Do, and Where It Falls Short

If you contribute to a 401(k) from every paycheck, you already use one of the simplest wealth-building strategies there is. It is called dollar-cost averaging, and it is how millions of Americans invest without ever trying to guess what the market will do next.

The idea is straightforward: invest the same amount of money at regular intervals, whatever prices are doing. What makes it powerful is less the maths than the behaviour it creates, because it keeps people investing through the moments when fear would otherwise make them stop.

This guide explains how dollar-cost averaging works, a worked example, what it can and cannot do, how it compares with investing a lump sum, how to set it up and the mistakes that undo it. FRC has no stake in what you buy: we do not sell investments, manage portfolios or earn commission, so everything here is explained impartially.

Watch the short version: the dollar-cost averaging video is in the FRC Retail Investing playlist on YouTube.

What Dollar-Cost Averaging Is

Dollar-cost averaging means investing a fixed dollar amount on a fixed schedule. For example, you might invest $200 into an S&P 500 ETF on the first day of every month, regardless of whether the market has risen or fallen.

Because the dollar amount stays the same, the number of shares you buy changes. When prices are high, $200 buys fewer shares, and when prices are low, the same $200 buys more.

Over time, that means you automatically buy more shares when the market is cheaper and fewer when it is more expensive. The approach was popularised decades ago by Benjamin Graham, often described as the father of value investing, as a disciplined way for ordinary investors to build positions over time.

If you are new to ETFs, FRC’s ETF Investing for Beginners course explains how they work and how to buy them. To build a regular investing plan into a complete portfolio, ETF Investing Strategies covers asset allocation and rebalancing.

A Simple Worked Example

Imagine you invest $100 a month into an ETF. In month one, the price is $20, so you buy five shares; in month two, it falls to $10, so you buy ten shares.

In month three, the price returns to $20, and you buy five more. You have invested $300 and own 20 shares, an average cost of $15 a share, even though the price was $20 in two of the three months.

That gap between your average cost and the average price is the arithmetic advantage of investing a fixed amount. When prices vary, a fixed dollar amount always buys proportionally more shares at the lower prices.

A Longer Example With a Market Dip

Now imagine $200 a month for five months, while the price moves from $50 to $40, down to $25, back to $40 and finally back to $50. Each month, $200 buys 4, 5, 8, 5 and 4 shares respectively.

After five months, you have invested $1,000 and own 26 shares, an average cost of about $38.46 a share. At the final price of $50, those shares are worth $1,300, a gain of 30 percent, even though the price ended exactly where it started.

An investor who put the full $1,000 in at $50 in month one would own 20 shares worth $1,000 at the end. In this example, the dip worked in the regular investor’s favour, but only because the price recovered.

Why Most People Already Do It

Contributing to a 401(k) from every paycheck is dollar-cost averaging. The same amount, or the same percentage of salary, goes in every pay period and buys whatever the plan’s funds cost on that day.

The same applies to automatic monthly investments into an IRA or a brokerage account. Many investors never make a conscious decision to dollar-cost average; it simply happens because they invest as they earn.

For most working people, regular investing is not a strategy chosen over a lump sum. It is the natural result of saving money from income as it arrives, which is why understanding it is so useful.

The Biggest Benefit Is Behavioural

The arithmetic advantage is real, but the bigger benefit is psychological. A fixed schedule removes the temptation to guess when the market will rise or fall, which even professional investors struggle to do consistently.

It also keeps you investing during downturns. When prices fall and headlines turn frightening, many people stop investing or sell, which is often exactly the wrong moment.

With a fixed schedule, the decision has already been made. Each contribution goes in automatically, and during a fall, it buys more shares than usual.

What Dollar-Cost Averaging Cannot Do

Dollar-cost averaging does not guarantee a profit. If you invest in something that falls and never recovers, regular investing simply means you keep buying an investment that is losing value.

It also does not protect against losses in a falling market. During a long decline, your balance will fall, even as you keep adding money.

The approach is most effective with broadly diversified investments, such as a total market or S&P 500 index fund, that have historically recovered from falls over time. It is far riskier when applied to a single stock or a narrow theme, where a permanent loss is more likely.

Lump Sum or Dollar-Cost Averaging?

A common question arises when someone already has a large sum to invest, such as an inheritance, a bonus or the proceeds of a sale. Should they invest it all at once or spread it out over time?

Historically, investing a lump sum straight away has more often produced the higher result. A Vanguard study comparing the two approaches across US, UK and Australian markets found that lump sum investing came out ahead about two-thirds of the time.

The reason is simple: markets have risen more often than they have fallen, so money invested earlier has had more time to grow. Holding cash while waiting to invest means missing out on gains more often than it avoids losses.

When Spreading It Out Still Makes Sense

The historical advantage of lump sum investing does not make dollar-cost averaging wrong. The remaining third of the time, investing gradually would have produced a better result, and no one knows in advance which situation they are in.

For many people, the bigger risk is regret. Investing a large sum just before a sharp fall can be so painful that some investors sell in a panic, turning a temporary fall into a permanent loss.

If spreading the money over several months is what allows you to invest with confidence and stay invested, it can be a reasonable trade-off. A defined schedule, such as equal amounts over six or twelve months, keeps the process disciplined.

How Dollar-Cost Averaging Performed in Real Downturns

In the 2008 financial crisis, the S&P 500 fell by more than half from its 2007 peak to its low in March 2009. Investors who kept contributing through that period were buying at some of the lowest prices in decades.

Recovery took several years, but those who kept investing through the fall had accumulated shares at low prices when the market eventually recovered. Investors who stopped or sold near the bottom often missed much of that recovery.

In early 2020, the market fell by about a third within weeks before rebounding within months. Again, regular investors bought through the fall, though past recoveries never guarantee future ones.

Missing the Best Days

One reason staying invested counts for so much is that many of the market’s strongest days have come close to its worst. Research by firms including J.P. Morgan Asset Management has shown that missing just a handful of the best days over a long period can sharply reduce long-term returns.

An investor who sells during a fall, intending to return when things feel safer, risks missing those rebound days. By the time confidence returns, prices have often already recovered.

Dollar-cost averaging helps avoid that trap. Because contributions continue on schedule, you remain invested through both the worst days and the best ones.

How to Set Up Dollar-Cost Averaging

Most US brokers make regular investing straightforward. You can schedule an automatic transfer from your bank account and an automatic purchase of a chosen ETF or mutual fund, weekly, every two weeks or monthly.

Many brokers also offer fractional shares, so a fixed dollar amount is fully invested even when one share costs more than your contribution. Without fractional shares, part of each contribution may sit as cash until it is large enough to buy a whole share.

Matching your investment schedule to your paycheck makes the habit easier to keep. Switching on automatic dividend reinvestment adds another layer, because each dividend payment then buys more shares as well.

Choosing What to Invest In

Dollar-cost averaging is a method, not an investment. It works alongside the choice of what to buy, and it suits broad, low-cost, diversified funds most.

Popular choices among US investors include total US market funds such as VTI and S&P 500 funds such as VOO, IVV or SPY. Some investors also add international and bond funds to build a more balanced portfolio.

FRC’s comparison of VOO, VTI and QQQ explains how three of the most popular ETFs differ. Check each fund’s website for current fees and holdings before you buy.

Which Account to Use

Regular investing works in any account, but the account changes how much tax you pay. A 401(k) is already set up for paycheck contributions, and many employers add a matching contribution.

An IRA, particularly a Roth IRA, lets growth compound without annual tax, and a monthly contribution of $500 adds up to $6,000 a year, within the 2026 IRA limit of $7,500. A taxable brokerage account has no contribution limit, but dividends and gains are taxed.

FRC’s guide to the order to invest your money between a 401(k), IRA and brokerage account explains how to decide where each dollar should go first.

Dollar-Cost Averaging Into Volatile Assets

Some investors use regular purchases for more volatile assets, such as spot bitcoin ETFs or sector funds. The larger the price swings, the bigger the difference between the average cost and the average price can be.

But volatility cuts both ways. Regular investing does not turn a speculative asset into a safe one, and an asset that falls sharply and stays down will still produce losses, however disciplined the schedule.

Many investors who dollar-cost average into volatile assets keep those positions small relative to a diversified core. FRC’s guide to bitcoin ETFs explains the risks of one of the most volatile funds available to US investors.

Reviewing Your Plan Once a Year

Automation does not mean ignoring your investments completely. A short review once a year keeps the plan on track without encouraging the frequent checking that leads to emotional decisions.

At each review, many investors check three things: whether the contribution amount can be increased, whether the mix of funds has drifted from its target, and whether fees or circumstances have changed. Rebalancing back to your target mix keeps risk at the level you chose.

Between reviews, the schedule does the work. Checking your balance every day adds stress without improving results, and it makes it harder to keep going during falls.

What Regular Investing Can Add Up To

Combined with compounding, regular investing can build substantial wealth over long periods. As an illustration, $500 a month for 30 years at a 7 percent average annual return would grow to roughly $610,000, from $180,000 of contributions.

Those figures assume smooth returns, which real markets never deliver, and they assume contributions never stop. Real results will vary, and past performance does not guarantee future returns.

FRC’s guides on how compound interest builds wealth in ETFs and how to invest $10,000 in ETFs explore these numbers in more detail.

Common Mistakes

The first mistake is stopping contributions during market falls. That is when each contribution buys the most shares, and stopping turns the strategy’s main advantage into a missed opportunity.

The second is leaving contributions sitting in cash because the automatic purchase was never set up. Money transferred into an account does not grow until it is actually invested.

The third is spreading a lump sum over such a long period, several years for example, that much of it misses out on growth. The fourth is using dollar-cost averaging on a single high-risk stock, and the fifth is never increasing the amount as income rises.

Questions to Ask Before You Start

First, are you investing from regular income, or do you already have a lump sum? The answer decides whether dollar-cost averaging is a natural habit or a deliberate choice.

Second, what will you invest in, and is it broadly diversified? Third, which account will you use, and is the purchase fully automated?

Fourth, can you commit to continuing through market falls? Finally, check each fund’s website for current fees, and confirm your broker is registered and a member of SIPC.

Common Questions

What is dollar-cost averaging in simple terms? It means investing the same amount of money at regular intervals, whatever the market is doing, so you buy more shares when prices are low and fewer when prices are high.

Is dollar-cost averaging better than investing a lump sum? Historically, lump sum investing has more often produced higher returns, about two-thirds of the time in Vanguard’s research. Dollar-cost averaging can still make sense if it helps you invest with confidence.

Does dollar-cost averaging guarantee a profit? No. It does not guarantee a profit or protect against losses in a falling market.

How often should I invest? Many investors match their schedule to their paycheck, investing weekly, every two weeks or monthly. Consistency counts for more than the exact frequency.

Is a 401(k) dollar-cost averaging? Yes. Contributing a fixed amount or percentage from every paycheck is a form of dollar-cost averaging.

Learning How to Build Wealth Is Open to Everyone

You do not need a finance background to use dollar-cost averaging well. Regular investing, diversification, account choice and staying the course can all be learned, and understanding them is what turns a monthly habit into long-term wealth.

FRC’s programmes and memberships are open to everyone. Start with ETF Investing for Beginners if you are new, move on to ETF Investing Strategies to build a complete portfolio, and continue to Advanced ETF Investing when you are ready to go deeper.

FRC’s Professional Membership adds structured learning, verified progress and a growing set of tools for investors who want to keep building their knowledge. The FRC dictionary, with explainer videos on the rules behind US investing, is free for everyone.

Your Next Step

Dollar-cost averaging turns investing into a habit rather than a series of difficult decisions. It is most effective with broad, low-cost funds, inside the right accounts, and with contributions that continue through every market fall.

Choose your fund, choose your account, automate the purchase and keep going. Then carry on with FRC’s complete step-by-step guide to investing in ETFs to build the rest of your portfolio.