Project the same amount invested every month at a flat annual return, with the year-by-year balance and a lump-sum contrast.
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Rows round to whole dollars; the headline keeps cents.
Each contribution goes in at the end of the month, so the monthly rate is the annual return divided by twelve. Contributions grow as the future value of an ordinary annuity: monthly amount times ((1 + monthly rate) raised to the number of months, minus 1), divided by the monthly rate. A starting balance compounds separately at that same monthly rate. Total contributed is the starting balance plus the monthly amount times the months, and growth is the ending balance minus that.
The lump-sum line grows the same total contributed once at the annual rate with yearly compounding. A monthly plan holds less money in the account during every early month, so the lump sum - more money at risk earlier - usually ends higher in this model. That is timing arithmetic, not a verdict: a real DCA-versus-lump-sum comparison depends on the order of returns, not just their average. A market that falls while you are still adding can leave the staggered plan ahead; one that climbs the whole way leaves the lump sum ahead. A flat rate shows you neither.
Defaults: $500 at the end of every month, 7% a year, 10 years, no starting balance. The monthly rate is 0.5833%; the balance ends at $86,542.40 on $60,000.00 contributed, so growth is $26,542.40, 44.2% on top of the money put in.
From the table: year 1 ends at $6,196 on $6,000 contributed (growth $196), year 5 at $35,796 on $30,000 (growth $5,796), year 10 at $86,542 (growth $26,542). Most of the dollars arrive late.
Same money, different timing: that $60,000.00 invested on day one at 7% with yearly compounding reaches $118,029.08, about $31,486.68 more, because all of it earned from the first day. If you do not have $60,000 on day one, you are not choosing between these two lines.
Nothing about sequence. A 7% average can be six good years and one crash, and the crash lands harder the larger your balance is by then.
It ignores fund fees, taxes, inflation, employer matching, dividends left in cash, and any month you skipped. The usual reason a real plan trails this table is contributions that stopped during a falling market.
Browser-only arithmetic: what you type stays on your device and is not sent anywhere. It models no specific security and knows nothing about your horizon or tax bracket; it is not a recommendation to invest a lump sum or spread money in. Capital in markets can lose value.