See how an initial deposit and regular monthly contributions grow over time with compound interest. Choose daily, monthly, quarterly or annual compounding and compare the balance year by year.
The compound interest formula
A lump sum grows as A = P(1 + r/n)nt. With monthly contributions, each deposit compounds from the month it is added. The longer the money stays invested, the more of the final balance comes from interest rather than deposits.
What your money could grow to
| Initial | Monthly | Rate | Time | Final balance | Interest earned |
|---|---|---|---|---|---|
| $0 | $500 | 7% | 10 yr | $86,542 | $26,542 |
| $0 | $500 | 7% | 20 yr | $260,463 | $140,463 |
| $0 | $500 | 7% | 30 yr | $609,985 | $429,985 |
| $10,000 | $0 | 7% | 20 yr | $40,387 | $30,387 |
| $10,000 | $500 | 5% | 20 yr | $232,643 | $102,643 |
Saving $500 a month at 7% grows to about $260,000 in 20 years — and more than doubles to around $610,000 in 30 years. The last ten years add more than the first twenty because of compounding.
The Rule of 72
Divide 72 by the annual rate to estimate how many years it takes money to double: at 6% about 12 years, at 8% about 9 years.
Frequently asked questions
Is daily compounding much better than monthly?
What return should I assume?
Does this include taxes and inflation?
Related calculators
Projections are hypothetical and not guaranteed. Not investment advice.
