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S&P 500 (SPY): which ended higher, investing monthly or all at once?

The same money put into SPY month by month or all on the first day, compared across many periods since 1993.

Confluence Zone operator · Data as of September 30, 2026 · Calculated October 1, 2026 · Recomputed monthly

Summary

With the same money ($60,000) going into SPY over 10 years from October 2016, putting it all in on the first day ended at $247,523, and spreading it over the months ended at $136,164.

Across 275 ten-year windows since 1993, all at once ended higher in 90% of them. The windows where monthly investing ended higher mostly started in 2000, 1999 and 2001, just before a large decline.

SPY, the same money monthly vs. all on the first day

Case	Put in	End balance	Return	Annual return (IRR)	Max drawdown	Max loss vs. money in
5 years, monthlyOct 2021 to Sep 2026	$30,000	$46,861	+56.2%	17.9%	−24.6%	−17.1%
5 years, all at onceOct 2021 to Sep 2026	$30,000	$56,588	+88.6%	13.5%	−24.5%	−16.1%
10 years, monthlyOct 2016 to Sep 2026	$60,000	$136,164	+126.9%	15.7%	−33.7%	−12.8%
10 years, all at onceOct 2016 to Sep 2026	$60,000	$247,523	+312.5%	15.2%	−33.7%	−3.5%
15 years, monthlyOct 2011 to Sep 2026	$90,000	$302,087	+235.7%	14.8%	−33.7%	−2.4%
15 years, all at onceOct 2011 to Sep 2026	$90,000	$789,928	+777.7%	15.6%	−33.7%	−2.4%
20 years, monthlyOct 2006 to Sep 2026	$120,000	$566,043	+371.7%	13.7%	−55.3%	−44.8%
20 years, all at onceOct 2006 to Sep 2026	$120,000	$984,840	+720.7%	11.1%	−55.2%	−46.6%

The annual return is based on how long the money was in the market, so its order can differ from the order of end balances.

Comparing 275 ten-year windows

	Value
Windows where all at once ended higher	248 (90%)
Windows where monthly ended higher	27

How it was calculated

Monthly investing put in $500 on the first trading day of each month, including the first month. All at once put the same total in on the first day.
Each buy or sell was charged 0.15% as a cost. Taxes, currency conversion costs and interest on cash are not included.
Dividends were reinvested at the price on each ex-dividend date. Taxes on dividends are not deducted.
Annual return (IRR) is the average yearly return that accounts for when each deposit went in. Max loss vs. money in is the largest gap by which the balance fell below the total put in up to that day.
The as-of date is the last trading day of last month (September 30, 2026). The numbers are recomputed at the start of each month.
Buy and sell decisions use the close, and trades fill at the next trading day's open. See the backtest spec

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Common questions

Was the loss against the money put in larger when investing all at once?

For the 10 years from Oct 2016 to Sep 2026, the max loss vs. money in was −12.8% for monthly investing and −3.5% for all at once. It varies by window, so neither side was always smaller.

Would the results change with an amount other than $500 a month?

In this SPY calculation, the returns stay almost the same and only the amounts scale. Only the basket method, which buys whole shares, differs a little.

Are dividends included?

Yes. This SPY calculation reinvests each dividend at the price on its ex-dividend date. Taxes on dividends are not deducted.

Would the result be the same when investing in a currency other than dollars?

No. This SPY calculation is in US dollars. Exchange rate changes and the fee and tax differences of locally listed ETFs are not included.