Compound Interest Calculator

See How Your Money Grows Over Time

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Compound Interest Calculator
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Interest Earned
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Total Contributions
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How to Use This Compound Interest Calculator

Our free compound interest calculator gives you accurate estimates in seconds. Enter your numbers above and hit Calculate — results update instantly.

All calculations use current 2026 rates and formulas. Results are estimates to help you plan — always verify with a licensed professional for final numbers.

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Frequently Asked Questions

What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest. Unlike simple interest, it causes your money to grow exponentially over time.
How often does interest compound?
Interest can compound daily, monthly, quarterly, or annually. The more frequently it compounds, the more you earn. Daily compounding yields slightly more than annual compounding.
What is the Rule of 72?
The Rule of 72 estimates how long it takes to double your money. Divide 72 by your annual interest rate. At 6% annual return, your money doubles in about 12 years (72 / 6 = 12).
What is a good interest rate for savings?
High-yield savings accounts in 2026 offer 4-5% APY. Long-term stock market average returns are around 7-10% annually. CDs offer 4-5% for fixed terms.
How does compound interest differ from simple interest?
Simple interest is only calculated on the principal. Compound interest is calculated on principal plus accumulated interest. On $10,000 at 5% for 10 years: simple = $5,000, compound = $6,289.

Compound Interest Calculator With Monthly Contributions

Use this compound interest calculator to estimate how your savings or investments may grow over time. You can compare the impact of starting balance, monthly contributions, interest rate, time horizon, and compounding frequency.

Daily, Monthly, and Yearly Compounding

Compound interest grows faster when interest is added more frequently. Daily compounding adds interest every day, monthly compounding adds it once per month, and yearly compounding adds it once per year. For the same interest rate and time period, more frequent compounding usually produces a higher final balance.

Investment Growth and Savings Goals

This calculator can help you estimate long-term investment growth, retirement savings, emergency fund growth, or a future savings goal. The monthly contribution field is especially important because regular deposits often have a larger long-term impact than the starting balance.

APY vs APR

APR is the stated annual interest rate before compounding. APY reflects the effective annual return after compounding. When interest compounds more frequently, APY is usually higher than APR.

Compound Interest Formula

A common compound interest formula is A = P(1 + r/n)^(nt), where P is the starting principal, r is the annual interest rate, n is the number of compounding periods per year, and t is the number of years. When monthly contributions are included, the final result also depends on the timing and size of each deposit.

FAQ

What is compound interest?

Compound interest is interest earned on both your original balance and the interest already added to it.

Is monthly compounding better than yearly compounding?

Usually yes. With the same rate and time period, monthly compounding normally produces a higher ending balance than yearly compounding.

Why do monthly contributions matter so much?

Monthly contributions add new principal regularly. Over long periods, those repeated deposits can compound and become a major part of the final balance.

What is the difference between APY and APR?

APR is the stated annual rate. APY includes the effect of compounding and better reflects the effective annual return.

Can I use this for investment planning?

Yes. It can estimate possible growth, but it does not predict market returns or guarantee investment performance.

Last checked: June 23, 2026