Use our Compound Interest Calculator to estimate how your money could grow over time through compound interest. Enter your initial investment, expected annual return, investment period, compounding frequency, and optional regular contributions.
This free calculator helps you estimate future value, total contributions, estimated growth, effective annual rate, and year-by-year compound growth.
Compound Interest Calculator
Enter your investment information below to estimate your future value.
Enter your information and click Calculate Compound Interest to see your estimated results.
Results are hypothetical estimates based on the assumptions entered. Actual returns may differ.
How to Use the Compound Interest Calculator
- Enter your initial investment.
- Enter your expected annual return.
- Enter your investment period in years.
- Select the compounding frequency.
- Enter an optional additional contribution.
- Select the contribution frequency.
- Click Calculate Compound Interest.
- Review your estimated future value, contributions, growth, effective annual rate, and yearly results.
What Is Compound Interest?
Compound interest is the process of earning returns on both the original amount of money and previously accumulated returns.
When earnings remain invested, they can become part of the balance used for future growth calculations. Over a long period, this can create a compounding effect.
Compound Interest Formula
The standard compound-interest formula for a lump-sum investment is:
FV = PV × (1 + r/n)nt
FV = Future Value
PV = Present Value or Initial Investment
r = Annual interest or return rate as a decimal
n = Number of compounding periods per year
t = Number of years
When regular contributions are included, the future value of those contributions is calculated separately and added to the future value of the initial investment.
How Additional Contributions Work
You can add regular contributions to your initial investment using the calculator.
Additional contributions are assumed to be made at the end of each selected contribution period.
For example, a $200 monthly contribution is treated as a $200 deposit at the end of every month.
Changing the timing of contributions can change the final result.
What Is Compounding Frequency?
Compounding frequency describes how often the assumed return is applied to the balance.
- Annually: 1 time per year
- Semiannually: 2 times per year
- Quarterly: 4 times per year
- Monthly: 12 times per year
- Daily: 365 times per year in this calculator
Daily compounding uses a 365-day assumption. Actual financial products may use different calculation conventions.
What Is the Effective Annual Rate?
The Effective Annual Rate (EAR) shows the annualized rate after accounting for the selected compounding frequency.
EAR = (1 + r/n)n − 1
For example, a nominal annual rate of 7% compounded monthly has an effective annual rate of approximately 7.23%.
Compound Interest vs. Simple Interest
Compound Interest
- Previously accumulated returns can contribute to future growth.
- Growth can accelerate over longer periods.
- Compounding frequency can affect the effective annual rate.
Simple Interest
- Interest is generally calculated using the original principal.
- Previously earned interest does not itself generate additional interest.
- Growth is generally more linear.
Why Time Matters With Compound Interest
Time can have a significant effect on compound growth.
When returns remain invested, each period can build on the previous balance. A longer investment period can therefore substantially change the estimated future value.
How the Expected Return Affects Growth
A higher assumed annual return generally produces a higher estimated future value when all other inputs remain unchanged.
However, higher potential returns can also involve greater investment risk. The rate entered into this calculator is a hypothetical assumption, not a guaranteed result.
Compound Interest Example
Suppose you start with $10,000, assume a 7% annual return, invest for 10 years, and use monthly compounding.
You can also add a regular contribution such as $200 per month to see how continued contributions may affect the estimated future value.
This is a hypothetical example. Actual investment returns are not guaranteed.
How Is Estimated Growth Calculated?
The calculator estimates growth by comparing the projected future value with the total amount contributed.
Estimated Growth = Future Value − Total Contributions
For investments, actual returns may come from interest, dividends, capital appreciation, or other sources. Therefore, "estimated growth" is a more general description of the result.
What Are Total Contributions?
Total contributions represent the money you put into the investment, excluding the growth generated by the assumed return.
Total Contributions = Initial Investment + Additional Contributions
Growth From Returns
The calculator also shows the estimated percentage of your total contributed amount represented by projected growth.
Growth Percentage = Estimated Growth ÷ Total Contributions × 100
What Is the Rule of 72?
The Rule of 72 is a simple method for estimating how long it could take money to double at a constant annual return.
Approximate Doubling Time = 72 ÷ Annual Return
For example, at an assumed 8% annual return, the Rule of 72 estimates approximately 9 years for money to double.
This is only a rough estimate and does not account for contributions, taxes, fees, inflation, or changing returns.
Compound Interest and Inflation
A future dollar amount may not have the same purchasing power as the same amount today.
Inflation can reduce purchasing power over time. This calculator does not automatically adjust the result for inflation.
Taxes and Investment Fees
Taxes, investment management fees, trading costs, account fees, and other expenses are not automatically deducted from the calculator's results.
Actual after-tax and after-fee results can therefore be lower than the hypothetical amount shown.
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Frequently Asked Questions
What is a Compound Interest Calculator?
A Compound Interest Calculator estimates how an initial investment and regular contributions could grow when an assumed return is compounded over time.
How does compound interest work?
Compound interest allows previously accumulated returns to become part of the balance used for future growth calculations.
Can I add monthly contributions?
Yes. You can add monthly, quarterly, semiannual, or annual contributions.
When are additional contributions made?
Additional contributions are assumed to be made at the end of each selected contribution period.
What happens if I enter 0%?
If the expected return is 0%, no compound growth is added. The future value equals the initial investment plus additional contributions.
What is the Effective Annual Rate?
The Effective Annual Rate represents the annualized rate after accounting for the selected compounding frequency.
Does the calculator include inflation?
No. Inflation is not automatically deducted from the projected future value.
Does the calculator include taxes and fees?
No. Taxes, investment fees, and other expenses are not automatically deducted.
Is the calculator result guaranteed?
No. The result is a mathematical estimate based on the assumptions entered. Actual investment returns may be higher or lower.
Compound Interest Calculator: The Bottom Line
Compound interest can help demonstrate how money may grow when returns remain invested and continue participating in future growth.
The main factors affecting the calculation are the initial investment, expected annual return, investment period, compounding frequency, and regular contributions.
Try different scenarios to understand how changing these assumptions affects the projected future value.
Revisiting Tools provides general informational and educational calculator tools. Results from this Compound Interest Calculator are estimates based on the information entered and should not be considered financial, investment, tax, legal, or professional advice.
Investment returns are not guaranteed. Actual results may differ substantially from the estimates shown.