Updated 2026-03-20 · Calculated at 7% average annual return (S&P 500 historical average)
See how $1,000 grows each year at 8% interest, comparing monthly vs annual compounding.
| Year | Principal | Interest Earned | Annual Compounding | Monthly Compounding |
|---|---|---|---|---|
| 1 | $1,000 | $83 | $1,080 | $1,083 |
| 2 | $1,000 | $173 | $1,166 | $1,173 |
| 3 | $1,000 | $270 | $1,260 | $1,270 |
| 4 | $1,000 | $376 | $1,360 | $1,376 |
| 5 | $1,000 | $490 | $1,469 | $1,490 |
With monthly compounding, your $1,000 grows to $1,490. With annual compounding, it grows to $1,469. The difference of $21 comes from interest earning interest more frequently.
Monthly compounding always produces a higher result because your interest starts earning its own interest 12 times per year instead of once.
A quick way to estimate how long your money takes to double: divide 72 by the interest rate. At 8%, your money doubles approximately every 9 years.
With monthly compounding, $1,000 at 8% annual interest grows to $1,490 after 5 years. That is $490 in interest earned. With annual compounding, you would get $1,469 — monthly compounding earns you an extra $21.
Using the Rule of 72, your money doubles in approximately 9 years at 8% annual interest. So $1,000 would become approximately $2,000 after 9 years.
Yes. A diversified stock market portfolio (S&P 500) has historically returned 7-10% annually. 8% is a reasonable assumption for long-term equity investing.
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