Compound Interest Calculator
See how an investment grows when interest compounds, with an optional yearly contribution.
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Formulas Used
- Compound interest
A = P × (1 + r/n)^(n×t)- Contributions
FV = PMT × [((1 + r/n)^(n×t) − 1) / (r/n)]
P is the principal, r the annual rate as a decimal, n the number of compounding periods per year and t the number of years. The annual contribution is split evenly across the periods and deposited at the end of each one.
How to use it
- Enter Your Values Input your numbers or parameters into the Compound Interest Calculator. Fill in all required fields for an accurate calculation.
- Calculate Results Click the calculate button to process your inputs. The Compound Interest Calculator delivers instant, accurate results.
- Review and Use Review your calculated results, explore the breakdown, and copy or share the output for your needs.
Tip Pair the Compound Interest Calculator with a spreadsheet — paste results directly into Excel or Google Sheets for further analysis.
Understanding Compound Interest
Compound interest is the process where the interest earned on an initial principal amount also earns interest over time. Unlike simple interest, which is calculated only on the original principal, compound interest grows exponentially because interest is calculated on the accumulated amount from previous periods.
The formula for compound interest is:
A = P times (1 + frac{r}{n})^{nt}
- A = the future value of the investment/loan, including interest
- P = the principal investment amount (initial deposit or loan)
- r = the annual interest rate (decimal)
- n = the number of times interest is compounded per year
- t = the number of years the money is invested or borrowed for
This calculation matters because it shows how investments grow over time, accounting for interest on interest. It is commonly used in savings accounts, retirement funds, loans, mortgages, and any financial product where interest accumulates periodically.
For example, if you invest $1,000 at an annual interest rate of 5%, compounded monthly, the compound interest formula calculates how much your investment will be worth after a certain number of years, considering the effect of monthly compounding.
What is Compound Interest?
Compound interest is the process where interest is earned on both the original principal and the accumulated interest from previous periods. This means your investment grows faster than with simple interest, which only calculates interest on the principal.
The formula used to calculate compound interest is A = P (1 + r/n)^{nt}, where each variable represents the principal, interest rate, compounding frequency, and time. Understanding this formula helps you predict how your money will grow over time.
When to Use a Compound Interest Calculator
- When you want to estimate the future value of a savings account or investment with periodic compounding.
- To plan for retirement by projecting how your contributions will grow over decades.
- To understand how much you will owe on a loan where interest compounds periodically.
- When comparing different financial products with varying compounding frequencies.
Common Mistakes to Avoid
- Entering the interest rate as a whole number instead of a decimal (e.g., 5 instead of 0.05).
- Mixing up the number of compounding periods per year with the total number of years.
- Assuming interest compounds annually without checking the actual compounding frequency.
Using a compound interest calculator correctly helps you make informed financial decisions by accurately projecting growth or debt over time.
Common use cases
- Saving for a 5-Year Goal
- Retirement Fund Growth Over 30 Years
Frequently asked questions
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