Dollar-Cost Averaging vs Lump Sum: What the Math Says
The Two Strategies in One Minute
Lump sum means putting the whole amount to work immediately. Monday morning, all EUR 24,000 into your chosen fund.
Dollar-cost averaging (DCA) means splitting the amount into equal instalments across a set period. EUR 2,000 a month for a year, or EUR 6,000 a quarter for four quarters.
Because the instalments are fixed in euros, they buy more units when prices are low and fewer when prices are high. Your average purchase price gets smoothed out. That is the whole mechanism, and everything else people claim about DCA follows from it.
What the Math Says
Markets rise more often than they fall, and money held back in cash is money not compounding. So the base case favours investing everything at once.
Vanguard tested this across seven markets over rolling one-year periods from 1976 to 2022. A lump sum produced the better outcome between 61.6% and 73.7% of the time, depending on the market. For a 100% equity portfolio the median advantage was 2.2% (Vanguard, The truth about cost averaging).
Call it roughly two thirds of the time. That is a strong tilt, not a certainty.
A Worked Example: The Ordinary Year
You have EUR 24,000 and a global equity ETF trading at EUR 100 a unit in January.
Prices through the year: EUR 100 in January, 105 in April, 110 in July, 115 in October, closing the year at 120.
Lump sum. EUR 24,000 buys 240 units at EUR 100. At year end those 240 units are worth EUR 28,800, a gain of EUR 4,800, or +20%.
DCA across four quarters. EUR 6,000 each time:
| Purchase | Price | Units bought |
|---|---|---|
| January | EUR 100 | 60.00 |
| April | EUR 105 | 57.14 |
| July | EUR 110 | 54.55 |
| October | EUR 115 | 52.17 |
| Total | 223.86 |
Those 223.86 units at EUR 120 come to EUR 26,863, a gain of EUR 2,863, or +11.9%.
The lump sum finishes EUR 1,937 ahead. Same money, same fund, same year. The only difference is that the lump sum was invested for all twelve months, while the DCA money was invested for an average of seven and a half months and sat in cash for the rest, missing part of the rise.
When DCA Wins
Now run the bad year. Same EUR 24,000, same ETF at EUR 100 in January. This time the market falls hard and only partly recovers: EUR 100 in January, 85 in April, 70 in July, 85 in October, closing at 95.
Lump sum. Those same 240 units, now at EUR 95, are worth EUR 22,800. A loss of EUR 1,200, or -5%.
DCA across four quarters:
| Purchase | Price | Units bought |
|---|---|---|
| January | EUR 100 | 60.00 |
| April | EUR 85 | 70.59 |
| July | EUR 70 | 85.71 |
| October | EUR 85 | 70.59 |
| Total | 286.89 |
Those 286.89 units at EUR 95 come to EUR 27,255, a gain of EUR 3,255, or +13.6%.
DCA finishes EUR 4,455 ahead and turns a losing year into a good one. The instalments kept buying while the price was down, so the same EUR 24,000 bought roughly 47 more units than the lump sum did.
The Argument the Numbers Miss
If the math were the whole story, this article would be one line long. It is not, for one reason: the best strategy is the one you can actually go through with.
Putting EUR 24,000 in on a Monday and watching it become EUR 19,000 by Friday is how people swear off investing altogether. If splitting the money into four instalments is what gets it invested at all, then the 2.2% median advantage you gave up is cheap insurance.
DCA is not a return strategy. It is a regret-management strategy. That is a perfectly reasonable thing to want, as long as you know that is what you are buying.
- Your horizon is long. Decades of compounding make a few bad months irrelevant.
- You have sat through a crash before without selling. You know your own reaction.
- The money is already earmarked for a portfolio you would hold regardless of entry point.
- The sum is large relative to your net worth. A bad first month would dominate everything else you own.
- You are new to investing and have not tested your own nerve yet.
- The alternative is doing nothing. Money in cash for a year loses to inflation with certainty, not just probability.
How to Tell Which One Worked for You
Most articles stop at the advice. But your own portfolio can answer this directly, using two return figures that measure different things.
Time-weighted return (TWR) strips your deposits out and measures how the holdings themselves performed. It is the fund's number.
Money-weighted return (MWR, also called IRR) accounts for the size and timing of every deposit, so it measures how you did.
Put them side by side and the gap between them is your timing, expressed as a number:
Say the fund returned 8% for the year and your own return was 11%. Those three points are what your deposit timing contributed. Had your return been 5% instead, timing cost you three points. Either way it is measured rather than guessed, which beats arguing about strategies in the abstract.
How Turbobulls Tracks This
You do not have to run any of this by hand. Turbobulls calculates ROI, money-weighted return (MWR/IRR) and time-weighted return (TWR) from your transaction history, so the timing gap above is something you read off a dashboard rather than something you theorise about.
Three things make the comparison usable:
- Both returns together. MWR and TWR are computed side by side, so the timing effect is visible without exporting anything to a spreadsheet.
- Benchmarks. Compare your portfolio against configurable benchmarks to see what the same stretch of market looked like without your cashflows in the way.
- Currencies handled properly. 30+ currencies, with FX applied on the trade date. If you averaged into a US-listed ETF from a euro account, the currency effect stays separated from the price effect instead of being quietly baked into one number.
One honest limit: Turbobulls is a tracker, not a simulator. It will not tell you what a lump sum would have done instead. It tells you precisely what your actual deposits did, which is the part you can learn from.
If you want a look before signing up, demo mode is read-only, needs no signup and runs for 30 minutes. The trial afterwards is 14 days with no credit card.
See What Your Timing Actually Cost or Earned
The Full Picture: Read These Next
MWR vs TWR - the two return figures that measure your timing
Max drawdown - how far your net worth fell, which is the fear DCA is answering
Return volatility - how jumpy the ride has been
Benchmark comparison - what the market did over the same period
Performance metrics guide - every return number in one place
Frequently Asked Questions
Q: Is dollar-cost averaging safer?
It reduces the impact of a single bad entry date, which is a real form of safety. It does not reduce the risk of holding the investment afterwards. Once the last instalment lands, both investors own exactly the same thing.Q: If I average in, over how long?
The longer the period, the more time your money spends in cash, and cash is where the historical disadvantage comes from. Most people who split a lump sum use somewhere between three and twelve months. There is no optimal figure, because the right answer depends on a market path nobody can see yet.Q: Does any of this change for ETFs versus individual stocks?
The mechanism is identical. The stakes are not. A single stock can fall and never recover, which makes a badly timed lump sum permanently bad. A broad index fund has historically recovered given enough time, which is part of why the lump-sum statistics look as favourable as they do.Q: What if the market drops right after I invest a lump sum?
Then you experience the roughly one third of cases where DCA would have been better. That outcome is inside the statistics, not an exception to them. What matters is whether you hold on, because the loss only becomes permanent when you sell.Turbobulls is a tracking and analytics tool, not an investment adviser. Nothing here is investment, tax, or legal advice. Investing involves risk, including loss of principal. Do your own research or consult a licensed professional.
Stop Guessing Whether Your Timing Helped
Turbobulls turns your transaction history into the return figures that answer this question for your actual portfolio, not a hypothetical one.
- Money-weighted and time-weighted returns computed side by side
- Configurable benchmarks to compare against the market over the same period
- Multi-currency portfolios with FX applied on the trade date
- Realized and unrealized gains split out, with the currency effect separated
- Zero manual calculations - log a transaction, see updated metrics
Get these by email
One useful investing metric, properly explained. Unsubscribe in one click.
Read more
MOIC Explained: How Many Times Over Did You Get Your Money Back?
MOIC (Multiple on Invested Capital) is what your portfolio is worth or has returned divided by what you put in. Learn what 1.42x means, how Turbobulls calculates it, and how it differs from MWR and ROI.
Return Volatility Explained: How Steady or Jumpy Are Your Returns?
Return volatility measures how much your annualised return has swung around its own average - the same dispersion that sits under the Sharpe ratio. Learn what it means, how Turbobulls calculates it, and why it is not the same as day-to-day price volatility.
Cost Efficiency Explained: How Much of Your Gains Actually Survive?
Cost efficiency measures the share of your investment gains that survives fees and taxes. Learn how Turbobulls calculates it, what good values look like, and why high costs quietly destroy long-term wealth.