Compound Interest Calculator
Calculate compound interest with optional monthly contributions. See year-by-year growth, total interest earned, and final balance.
Final Balance
$54,915.51
Total Interest Earned
$20,915.51
Total Contributions
$34,000.00
Growth Breakdown
Year-by-Year Breakdown
| Year | Balance | Contributions | Interest | Growth |
|---|---|---|---|---|
| 1 | $13,215.88 | $12,400.00 | $815.88 | |
| 2 | $16,664.23 | $14,800.00 | $1,864.23 | |
| 3 | $20,361.86 | $17,200.00 | $3,161.86 | |
| 4 | $24,326.80 | $19,600.00 | $4,726.80 | |
| 5 | $28,578.36 | $22,000.00 | $6,578.36 | |
| 6 | $33,137.26 | $24,400.00 | $8,737.26 | |
| 7 | $38,025.74 | $26,800.00 | $11,225.74 | |
| 8 | $43,267.59 | $29,200.00 | $14,067.59 | |
| 9 | $48,888.39 | $31,600.00 | $17,288.39 | |
| 10 | $54,915.51 | $34,000.00 | $20,915.51 |
About Compound Interest Calculator
This compound interest calculator helps you project how your savings or investments will grow over time. Enter your initial deposit, annual interest rate, compounding frequency, and time period to see a detailed breakdown of your investment's growth trajectory.
How Compound Interest Works
Compound interest is earned on both your original principal and on interest that has already been added to your balance. The formula is A = P(1 + r/n)^(nt), where P is the principal, r is the annual rate, n is the compounding frequency, and t is time in years. This exponential growth is what makes long-term investing so powerful.
Monthly Contributions
The calculator includes an optional monthly contribution field that lets you model regular deposits. Adding even a modest amount each month can significantly increase your final balance, as each contribution begins earning compound interest from the moment it is added.
Year-by-Year Breakdown
A detailed table shows your balance at the end of each year, along with the total contributions and total interest earned up to that point. This makes it easy to see how your money grows and at what point compound growth begins to accelerate.
Common Uses
- Planning retirement savings and 401(k) projections
- Comparing different savings account interest rates
- Modeling investment growth for financial goals
- Understanding the impact of different compounding frequencies
- Calculating how long it takes to reach a savings target
All calculations run entirely in your browser. No financial data is transmitted or stored.
Frequently Asked Questions
What is compound interest and how does it differ from simple interest?
Compound interest is calculated on both the initial principal and the accumulated interest from previous periods, while simple interest is only calculated on the principal. Over time, compounding causes your money to grow exponentially rather than linearly, which is why it is sometimes called "interest on interest."
How does compounding frequency affect my returns?
More frequent compounding (daily vs. yearly) results in slightly higher returns because interest is calculated and added to the principal more often. Daily compounding earns more than monthly, which earns more than quarterly, which earns more than yearly. However, the differences become smaller as frequency increases.
How do regular monthly contributions impact compound interest growth?
Adding regular monthly contributions dramatically accelerates growth because each deposit starts earning compound interest immediately. Even small consistent contributions can outpace a larger initial deposit over long time horizons due to the compounding effect on each contribution.
What is the Rule of 72 and how does it relate to compound interest?
The Rule of 72 is a quick estimation method. Divide 72 by the annual interest rate to approximate how many years it takes to double your money. For example, at 8% interest, your money roughly doubles every 9 years (72 / 8 = 9). This calculator provides exact figures for any scenario.