Saving $100 a month for 30 years means putting in $36,000. At an 8% annual return, the balance reaches $149,036, so $113,036 (76%) comes from growth rather than your own deposits.
Balance by years and return
| Time | You deposit | 4% return | 6% return | 8% return | 10% return |
|---|---|---|---|---|---|
| 10 years | $12,000 | $14,725 | $16,388 | $18,295 | $20,484 |
| 20 years | $24,000 | $36,677 | $46,204 | $58,902 | $75,937 |
| 30 years | $36,000 | $69,405 | $100,452 | $149,036 | $226,049 |
| 40 years | $48,000 | $118,196 | $199,149 | $349,101 | $632,408 |
The right-hand columns climb faster than the deposits. In the 40-year row at 10%, growth is 92% of the balance, while at 4% over 10 years it is only 19%. Time matters more than the monthly figure at the start.
What we assumed
- Returns are an assumed constant annual rate compounded monthly. Real markets vary year to year.
- Deposits are made at the end of each month unless stated.
- Taxes, fees and inflation are ignored unless the table says otherwise.
Related calculators: Compound Interest Calculator, Credit Card Payoff Calculator.
Questions people ask
Is 8% realistic?
Long-run US stock market returns have been in that range before inflation, but not in every decade. Use the 4% and 6% columns as a conservative check.
What if I miss some months?
Missed months reduce the balance a little each time. Use the calculator to model a lower average deposit.
Estimates for general education, not financial, tax or legal advice. Real results depend on your lender, employer, tax situation and location. See the disclaimer.