Starting Early vs Starting Late

By Nathan Hays · Updated July 31, 2026

This page is arithmetic, not advice. It answers one question with numbers: over a fixed thirty-year window, how much does the position of your deposits inside that window change the ending balance, holding the deposit amount and the rate constant? Every figure comes from the engine behind the free compound interest calculator, so you can reproduce any of them yourself.

The setup

Both savers use identical terms: $300 a month, an illustrative 7% annual rate, monthly compounding, deposits credited at the end of each month, no starting balance, and the same measurement date at the end of year thirty. Nothing differs except when the deposits happen. The illustrative rate is held constant so that timing is the only variable; real returns are not constant, and that caveat applies to every figure on this page.

The early saver's balance is computed in two stages, exactly as you would do it in the calculator: run $300 a month for ten years, then take the resulting balance, enter it as a starting amount with a monthly deposit of zero, and run it for twenty more years.

The classic comparison, computed

The early saver stopped depositing at year ten with $51,925.44. That balance then grew untouched for twenty years at 7% compounded monthly, reaching $209,713.30 without another dollar being added. The late saver deposited $36,000 more in total and still finished $53,435.30 lower.

The reason is dull and complete: the early saver's dollars were exposed to compounding for an average of about twenty-five years, while the late saver's were exposed for about ten. Compounding is exponential in time and merely linear in the amount deposited, so time wins whenever the two are traded against each other over a long enough window.

For reference, a saver who deposited $300 a month for all thirty years would put in $108,000 and finish at $365,991.30. That is the ceiling this comparison sits under.

It is worth being precise about what the early saver did and did not do. They did not earn a better rate, choose better accounts, or deposit more money. They deposited less, for a shorter period, and then stopped. The only advantage was position inside the window, and that single advantage was worth $53,435.30 against a saver who put in twice as much. This is the cleanest demonstration available that the compounding curve rewards the number of periods a dollar experiences, not the number of dollars deposited.

What the catch-up costs

Suppose the late saver wants the early saver's ending balance, using the same rate and the same twenty-year window from year eleven to year thirty. Because the future value of a deposit stream is directly proportional to the deposit, the required amount is a single division. One dollar a month for twenty years at 7% compounded monthly grows to $520.93, so:

$209,713.30 ÷ $520.93 = $402.58 per month

Feeding $402.58 a month back through the engine for twenty years returns $209,713.30, confirming the division. That is 1.34 times the early saver's monthly deposit, and it totals $96,619 of deposits against the early saver's $36,000. The late saver must put in $60,619 more to arrive at the same place.

The cost of each year of delay

The same window, the same $300 a month, the same 7%, varying only the starting year. Each row deposits through the end of year thirty.

A single year of delay costs $28,141.00 at the end, against $3,600 of deposits not made. Five years of delay costs $122,969.79 against $18,000 not deposited. The ratio of outcome lost to money not deposited is about 7.8 to 1 for the single year and about 6.8 to 1 for the five, because the very first dollars skipped are the ones that would have compounded the longest.

A version without the trick

The headline comparison is dramatic partly because one saver stops. Here is a milder setup where both savers deposit for exactly twenty years and put in exactly $72,000, measured at the same year-thirty date:

• Saver A deposits $300 a month in years 1 through 20, reaching $156,278.00, then leaves the balance alone for ten years. Ending balance: $314,065.86.
• Saver B deposits $300 a month in years 11 through 30. Ending balance: $156,278.00.

Same deposit, same number of deposits, same total dollars, same measurement date. The ten-year head start is worth $157,787.86, which is 101% more than saver B ended with. Saver A's twenty years of deposits and saver B's twenty years of deposits are the same $156,278.00 at the moment the last one lands; the head start is entirely the ten years that followed.

What this page is and is not

Everything above is time-value arithmetic on an assumed constant rate. It is not a projection of anyone's savings, it does not assume any particular account or product, and 7% is used only because it makes the comparison legible next to the other worked examples on this site. Substitute any rate you like; the ordering of the results does not change, only their size. Real returns vary from year to year and can be negative, which means an actual outcome will not trace a smooth curve even if its long-run average matches the assumption.

The one durable conclusion is structural rather than personal: in a fixed window, dollars deposited earlier are worth more at the end than identical dollars deposited later, and the multiplier is exponential in the time between them.

Frequently asked questions

Related reading: Monthly contributions · How compound interest works · The Rule of 72 · How fees compound · Inflation and compound interest · Glossary

All rates on this page are illustrative and assumed constant so that timing is the only variable. Real returns vary and can be negative. Nothing here is a projection, a recommendation, or investment, tax, or financial advice.