How the monthly savings calculator works
The two engines and their handoff
In year 1 of a $500/month plan, deposits are ~99% of the growth. By year 25 at 7%, the market's cumulative share approaches half the balance and climbing. The handoff is invisible month to month and decisive decade to decade — which is why contribution discipline early and patience late are the same skill seen from different ends.
Why monthly beats timing
Regular contributions are dollar-cost averaging by accident: you buy more shares when prices dip and fewer at peaks, and you never have to guess. The alternative — waiting to invest lump sums at "good" times — mostly waits. The market's best days cluster near its worst, and the disciplined monthly transfer catches both without watching.
Raising the number that matters
A 1% of salary increase per year (automated) raises contributions ~8% annually for a median earner without a lifestyle shock. Compounding the contributions — not just the returns — is the quiet superpower of the 25-year column.