Compound Interest Calculator

See exactly how your money grows over time with the power of compound interest. Add regular contributions to see your full savings potential.

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Final balance
Total deposited
Interest earned
Year by year growth
YearBalanceDepositedInterest earned

The power of compound interest

Albert Einstein reportedly called compound interest the eighth wonder of the world. With compound interest, you earn interest not just on your initial deposit but on all the interest you have already earned — creating an exponential growth curve over time.

A = P(1 + r/n)^(nt)
A = final amount, P = principal, r = annual rate,
n = compounds per year, t = years

How to use this calculator for a realistic savings plan

Start with the amount you already have saved, then enter a contribution you could make in ordinary months—not an idealized number. The most useful projection is one you can sustain through rent increases, holidays, repairs, and other real-life costs.

Test a range of return rates instead of relying on a single optimistic estimate. Savings accounts, bonds, and market investments behave differently, and investment returns are never guaranteed. A lower-rate scenario shows whether your goal still works if results are less favorable than hoped.

Compare the impact of time and contributions. An extra year of saving and a modest recurring deposit can matter more than trying to chase a higher return. This calculator is for education and planning; it does not account for taxes, fees, inflation, or changes in contributions.

For a worked example, read How Compound Interest Works.

Frequently asked questions

What is the Rule of 72?
Divide 72 by your annual interest rate to estimate how many years it takes your money to double. At 7% interest, your money doubles roughly every 10.3 years (72 / 7 = 10.3).
How much should I save monthly?
Financial advisors often suggest saving 15-20% of your income for retirement. Even small amounts matter enormously due to compounding — $200/month at 7% for 30 years grows to over $227,000.
What return rate should I use?
The S&P 500 has historically averaged about 10% annually before inflation, or about 7% after inflation. For conservative estimates, use 4-6%; for moderate, use 7-8%; for aggressive, use 9-10%.