Compound Interest Calculator
Compound Interest Calculator
See how your savings grow over time with compound interest. Add a starting amount and regular monthly deposits, then watch the interest build year by year.
View year-by-year growth
| Year | You put in | Interest earned | Balance |
|---|---|---|---|
| Enter a number of years to see growth. | |||
How to Use the Compound Interest Calculator
Enter a starting amount, how much you’ll add each month, your expected annual interest rate, and how many years you’ll keep saving. The calculator instantly shows your future balance, how much of it came from your own deposits, and how much the interest added on top. Open the schedule to watch the balance grow year by year.
What Is Compound Interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Over time this snowballs — each year’s interest becomes part of the balance that earns interest the next year. The longer your money compounds, the more dramatic the growth, which is why starting early matters far more than starting big.
How Compounding Frequency Affects Growth
The more often interest is added, the faster your balance grows. Daily compounding earns slightly more than monthly, which earns more than annually, even at the same rate. The difference is small over a year but adds up over decades. Regular monthly contributions amplify the effect, because each deposit starts compounding the moment it lands.
Frequently Asked Questions
What is the formula for compound interest?
The basic formula is A = P(1 + r/n)^(nt), where P is the principal, r is the annual rate, n is how often it compounds per year, and t is the number of years. This calculator also adds your monthly contributions on top.
How is compound interest different from simple interest?
Simple interest is paid only on your original amount. Compound interest is paid on your original amount plus all the interest already earned, so it grows faster over time.
Does adding money monthly really make a difference?
Yes, a large one. Small regular contributions compound alongside your starting balance, and over many years they often add up to more than the interest on the principal alone.
Is anything I enter saved?
No. All calculations happen in your browser. Nothing you type is stored or sent anywhere.