How Much Will My Investment Grow with Compound Interest?
Enter a starting amount, annual interest rate, and time horizon — see your final balance and a year-by-year growth breakdown. Compare compounding frequencies to see the difference.
How compound interest works
With compound interest, your returns earn returns. Each period, the interest earned is added to your principal, and the next period's interest is calculated on the new, larger balance. The longer the time horizon, the more dramatic this effect becomes.
Compounding frequency matters, but less than most people expect. The real driver of growth is time and rate — even a 1% higher annual return makes a large difference over 20–30 years.
Example growth at 7% annual return (monthly compounding)
Starting with $10,000. No additional contributions.
10 years
$10,000 · 7% · monthly
$20,097
Interest earned: $10,097
20 years
$10,000 · 7% · monthly
$40,388
Interest earned: $30,388
15 years at 10%
$10,000 · 10% · monthly
$44,539
Interest earned: $34,539
Frequently asked questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from prior periods. Unlike simple interest, it causes investments to grow exponentially over time.
What is the difference between compounding frequencies?
More frequent compounding results in slightly higher returns. Daily compounding earns marginally more than annual compounding at the same interest rate, because interest is added to principal more often.
What is the Rule of 72?
Divide 72 by your annual interest rate to estimate how many years it takes to double your investment. For example, at 8% annual return your money doubles in about 9 years (72 ÷ 8 = 9).
Does this calculator account for inflation?
No. The results shown are nominal (not inflation-adjusted). To estimate real returns, subtract the expected inflation rate from your annual interest rate before calculating.
Disclaimer: Hypothetical results only. Does not account for taxes on gains, inflation, or fund fees. Not a guarantee of future investment returns.
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What Is Compound Interest?How compound interest grows your money exponentially over time.Compound vs Simple InterestLearn the key difference and when each type applies.How Much Should You Save for Retirement?The 4% rule, age-based milestones, and how to close the gap.How Does Inflation Erode Your Savings?Why cash loses value over time and what you can do about it.