“I’ll start investing next year” is the most expensive free sentence in personal finance. Nothing happens when you say it. No bill arrives. And yet it has a precise price: the growth your earliest contributions never get to do — the years of compounding you can’t buy back later at any wage. This calculator puts a number on it.
How it works
It compares two versions of you with the same end date: one starts contributing today, the other waits some years and then contributes the same monthly amount until the same date. Both run on compound growth over monthly contributions:
final value = contribution × [(1 + r)ⁿ − 1] / r, where r is the monthly rate and n the months invested
The difference between the two outcomes is the cost of waiting — but read it carefully, because it isn’t all loss, and the calculator splits it into two honest lines.
The honest math
$200 a month, an assumed 7% return, a 30-year horizon. Start today and you end with about $243,994. Wait five years, then contribute the same $200 a month, and you end with about $162,014. The gap: $81,980.
But $12,000 of that is simply deposits you never made ($200 × 60 months) — money that stayed in your pocket. The real cost of waiting is the rest: $69,980 of lost growth, roughly $14,000 for every year of delay. Even a single year of “let me think about it” deletes about $16,400 of growth, because what disappears are the final years of the curve — the ones where the balance is biggest and compounding works hardest.
Now in this site’s preferred unit. At a real hourly wage of $25, that $69,980 of lost growth is 2,800 hours — about a year and four months of full-time work, done at a desk to replace money that time would have made for free. Each year of delay costs about 560 hours: fourteen working weeks.
Why we wait anyway
The delay feels free because its cost is invisible and far away — nobody sends you a statement for growth that didn’t happen. Psychologists call it present bias: a small effort today (opening the account, automating the transfer) outweighs a large but distant reward. Which points to the fix: don’t wait for the perfect moment or the “right” amount — make starting so small and automatic that it needs no willpower at all.
Worth keeping in mind
- The return is an assumption. 7% is a long-run guess you can change, not a promise. Markets fall as well as rise, and short horizons feel every dip.
- Starting small beats waiting big. With these numbers, $100 a month started today ends ahead of $200 a month started ten years from now. Half the effort, better outcome — try the combinations above.
- It cuts both ways. Money you’ll need soon doesn’t belong in this math: a short horizon is a reason not to invest it, not a reason to hurry.
To watch a plan that starts today grow year by year, use the compound interest calculator; for what a recurring expense steals, the cost of a habit. Up above, try moving only the “years you wait” field and watch the lost-growth line. That’s the price tag on “next year” — finally visible.