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Compound Interest Calculator

Calculate growth of investments with compound interest

Compound Interest Calculator

Principal ($)

Annual Interest Rate (%)

Years

Compound Frequency

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About This Calculator

A compound interest calculator shows how your money grows over time when interest is earned on both the principal and previously accumulated interest. The formula is A = P(1 + r/n)^(nt), where P is the principal, r is the annual interest rate, n is the number of compounding periods per year, and t is the number of years. For example, $10,000 invested at 7% annual return compounded monthly for 20 years grows to about $40,387 — more than quadrupling without any additional contributions. This calculator lets you experiment with different principal amounts, interest rates, and compounding frequencies (daily, monthly, quarterly, annually) to see projected future values. It is essential for understanding investment growth, comparing savings accounts, evaluating the true cost of debt, and planning long-term financial goals. Albert Einstein reportedly called compound interest the "eighth wonder of the world" — and seeing the numbers makes clear why. The earlier you start investing, the more time compounding has to work, which is why this tool often motivates people to begin saving immediately.

How to Use

1
Enter investment details
Input your initial principal and annual interest rate.
2
Set the time period
Choose the investment duration and compounding frequency.
3
View growth chart
See your total balance, interest earned, and a year-by-year growth breakdown.

Frequently Asked Questions

Q. What is the difference between simple and compound interest?

Simple interest is calculated only on the original principal (Interest = P × r × t), while compound interest is calculated on the principal plus all previously earned interest. Over time, compound interest grows exponentially while simple interest grows linearly. A $10,000 investment at 5% over 20 years earns $10,000 in simple interest but about $16,533 in compound interest.

Q. How often should interest be compounded?

More frequent compounding produces slightly higher returns. Daily compounding yields more than monthly, which yields more than annually. However, the differences are often small — the jump from annual to monthly compounding matters more than monthly to daily. Most savings accounts compound daily, while many investments compound annually.

Q. What is the Rule of 72?

The Rule of 72 is a quick way to estimate how long it takes to double your money: divide 72 by your annual interest rate. At 8% returns, your money doubles in approximately 72/8 = 9 years. At 6%, it takes about 12 years. This rule works best for rates between 4% and 12%.

Q. How much will $10,000 grow in 30 years?

At a 7% annual return compounded annually, $10,000 grows to about $76,123 in 30 years. At 10%, it reaches roughly $174,494. Adding $200 per month at 7% would grow to approximately $283,000. The length of time invested is the most powerful variable in compound interest calculations.

Disclaimer: Results are for informational purposes only and do not constitute professional advice. Always consult qualified professionals for important decisions.

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