FINANCIAL CALCULATOR
Compound Interest Calculator
Estimate how an initial investment and regular monthly contributions could grow with compound interest. Compare different interest rates, investment periods, and compounding frequencies.
Investment Growth Inputs
Modify the values and click Calculate to update the estimate.
Investment Summary
Estimated value of your investment over the selected period.
| Cost | Amount |
|---|---|
| Initial Investment | $10,000.00 |
| Monthly Contributions | $24,000.00 |
| Total Contributions | $34,000.00 |
| Interest Earned | $20,713.58 |
| Final Balance | $54,713.58 |
Where Your Money Goes
Contributions compared with estimated interest.
Growth Summary
Key figures from your investment scenario.
Estimated Growth Over Time
Estimated balance at the end of each year.
| Year | Estimated Balance | Total Contributions | Interest Earned |
|---|---|---|---|
| 0 | $10,000.00 | $10,000.00 | $0.00 |
| 1 | $13,201.42 | $12,400.00 | $801.42 |
| 2 | $16,634.27 | $14,800.00 | $1,834.27 |
| 3 | $20,315.28 | $17,200.00 | $3,115.28 |
| 4 | $24,262.39 | $19,600.00 | $4,662.39 |
| 5 | $28,494.83 | $22,000.00 | $6,494.83 |
| 6 | $33,033.24 | $24,400.00 | $8,633.24 |
| 7 | $37,899.74 | $26,800.00 | $11,099.74 |
| 8 | $43,118.03 | $29,200.00 | $13,918.03 |
| 9 | $48,713.55 | $31,600.00 | $17,113.55 |
| 10 | $54,713.58 | $34,000.00 | $20,713.58 |
This calculator provides a mathematical estimate based on the information entered. Actual investment returns may vary and are not guaranteed. Taxes, fees, inflation, withdrawals, and changes in investment performance are not included.
How to Use This Compound Interest Calculator
Enter your initial investment, monthly contribution, expected annual interest rate, investment period, and compounding frequency. The calculator estimates your future balance and separates the amount you contributed from the interest earned.
Change the inputs to compare different saving and investing scenarios. A longer investment period or larger regular contribution can substantially change the estimated future balance because money remains invested for more time.
If you are comparing borrowing costs rather than investment growth, you can also use our Loan Calculator to estimate loan payments and total interest.
What Is Compound Interest?
Compound interest is interest earned on both the original principal and interest that has already been added to the account. Instead of calculating growth only on the starting amount, compounding allows previous interest to become part of the balance that can earn additional interest.
The effect can become more noticeable over longer periods because each period's growth can contribute to future growth.
For comparison, Interest Calculator can be useful when you want to examine a simpler interest calculation without the same compounding effect.
What Does the Calculator Show?
- Estimated future balance
- Total contributions
- Total interest earned
- Starting investment
- Additional monthly contributions
Compound Interest Formula
For a single initial investment with no additional contributions, the standard compound interest formula is:
A = P(1 + r/n)^(nt)
In this formula, A is the future value, P is the initial principal, r is the annual interest rate expressed as a decimal, n is the number of compounding periods per year, and t is the number of years.
When monthly contributions are included, each contribution is also allowed to grow for the portion of the investment period during which it remains invested. This calculator assumes contributions are made at the end of each month.
Compound Interest Example
Suppose you start with $10,000, contribute $200 per month, and assume a 7% annual rate for 10 years with monthly compounding.
You would contribute a total of $34,000 over the 10-year period: $10,000 initially plus $200 for each of 120 months. Under the calculator's assumptions, the estimated future balance is approximately $54,713.58, including approximately $20,713.58 in estimated interest.
This is an illustrative calculation, not a prediction of actual investment performance. Real returns can vary from year to year, and investment products may have fees, taxes, and other costs.
How Compounding Frequency Affects Growth
Compounding frequency describes how often interest is added to the balance. Common frequencies include annual, semi-annual, quarterly, monthly, and daily compounding.
When the stated annual rate is the same, more frequent compounding can produce a different effective return because interest is added to the balance more often. The difference depends on the rate, time period, and compounding schedule.
If you want to compare this with a standard interest calculation, visit our Interest Calculator.
Why Time Matters With Compound Interest
Time can have a major effect on compound growth. When money stays invested for a longer period, previously earned interest has more opportunities to become part of the balance and generate additional growth.
This is why comparing the same contribution and interest-rate assumptions over different time periods can produce very different estimated balances.
How Monthly Contributions Affect Growth
Regular contributions increase the amount of money invested over time. Each contribution can then participate in future growth for the portion of the investment period during which it remains in the account.
Increasing the monthly contribution can therefore affect the final balance through both additional money contributed and additional interest earned on that money.
Compound Interest vs. Simple Interest
Simple interest is generally calculated only on the original principal, while compound interest allows previously earned interest to contribute to the balance used for future growth.
The difference can become more significant as the investment period increases, although the actual result depends on the rate, compounding schedule, contributions, and other account terms.
To explore a simpler interest calculation, use our Interest Calculator.
What This Calculator Does Not Include
This calculator provides a mathematical estimate based on the assumptions you enter. It does not account for investment fees, taxes, inflation, market volatility, changes in interest rates, withdrawals, or other account-specific conditions.
Investment returns are not guaranteed. For investments tied to market performance, actual results may be higher or lower than the assumed rate used in the calculation.
Frequently Asked Questions
What is the difference between simple and compound interest?
Simple interest is generally based on the original principal, while compound interest allows previously earned interest to become part of the balance that can earn additional interest.
You can compare the two approaches using the Interest Calculator and this Compound Interest Calculator.
How does compounding frequency affect investment growth?
Compounding frequency determines how often interest is added to the balance. With the same stated annual rate, changing the compounding frequency can change the effective growth of the account.
Does this calculator guarantee investment returns?
No. The calculator provides a mathematical estimate based on the assumptions entered. Actual investment returns can vary, and investments may lose value.
Why do regular contributions matter?
Regular contributions increase the amount invested over time. Each contribution can potentially earn returns for the portion of the investment period during which it remains invested.
What happens if the interest rate is 0%?
With a 0% interest rate, no interest is earned. The final balance is simply the initial investment plus all monthly contributions.
Can I use this calculator for savings accounts?
You can use it for an account when the assumptions match the account's interest rate, compounding schedule, contribution timing, and other applicable terms. Actual bank calculations may differ depending on the account rules.