Compound Interest Calculator
Calculate compound interest and investment growth
Investment details
Growth calculation notes
- The calculation assumes a constant rate throughout the modeled period.
- Recurring contributions are normalized to each compounding period.
- Higher frequency changes the result at the same stated annual rate.
- Taxes, fees and inflation are not included in this projection.
- A negative modeled balance means planned withdrawals exceed the funding in this model.
Investment summary
Enter your details to calculate the result.
- Final amount
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- Net interest
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- Initial principal
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- Additional contributions
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- Total contributions
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Investment growth chart
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Enter your details to calculate the result.
Year-by-year growth
| Year | Starting amount | Contributions | Interest earned | Ending amount |
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About Compound Interest Calculator
Our free compound interest calculator shows you exactly how your money grows over time through the power of compounding. Enter your initial investment, interest rate, time period, and optional regular contributions to see your projected final investment value, total interest earned, and a detailed year-by-year growth breakdown. This is the essential tool for anyone planning for retirement, saving for education, or building long-term wealth.
The calculator uses the standard compound interest formula A = P(1 + r/n)^(nt) to compute growth across six compounding frequencies: annually, semi-annually, quarterly, monthly, weekly, and daily. When you add regular contributions, the model spreads the annualized contribution across compounding periods and adds it at each period’s end. A fractional final period uses prorated time and a proportional final contribution. Actual deposit timing can produce different results.
With support for 40+ world currencies, flexible contribution frequencies, and export options in CSV, TXT, and PNG chart formats, this calculator serves investors, financial planners, students, and anyone who wants to understand the time value of money. No financial data you enter is ever sent to a server.
Key Features
- Compound Interest Formula: Accurate calculations using A = P(1 + r/n)^(nt) with support for any principal, rate, and time period
- Six Compounding Frequencies: Choose from annually, semi-annually, quarterly, monthly, weekly, or daily compounding
- Regular Contributions: Add recurring deposits with annual, quarterly, monthly, or weekly contribution frequencies
- Year-by-Year Breakdown: Detailed table showing starting balance, contributions, interest earned, and ending balance for each year
- 40+ Currency Support: Display results in USD, EUR, GBP, JPY, CAD, AUD, CHF, INR, TRY, BRL, and many more
- Investment Summary: Shows final amount, total interest earned, initial principal, additional contributions, and total contributions at a glance
- CSV Export: Download the year-by-year growth data as a CSV file for spreadsheet analysis
- TXT Export: Export a formatted text report with investment parameters and complete growth table
- PNG Chart Export: Generate and download a visual growth chart showing investment value over time
- Instant Results: All calculations are performed instantly with no loading delays
How to Calculate Compound Interest
- Select your currency: Choose from 40+ world currencies for properly formatted results.
- Enter the initial principal: Type the starting amount of your investment or savings.
- Set the annual interest rate: Enter the expected annual return rate as a percentage (e.g., 7 for 7%).
- Enter the time period: Specify how many years you plan to invest or save.
- Choose compounding frequency: Select how often interest is compounded -- daily compounding yields slightly more than annual.
- Add contributions (optional): Enter a regular contribution amount and select the frequency (annually, quarterly, monthly, or weekly) to see how additional deposits amplify growth.
Use Cases
- Retirement Planning: Project how much your 401(k), IRA, or pension fund will grow with regular contributions and compound returns over 20-40 years.
- Education Fund Savings: Calculate how much to save monthly to reach a college tuition goal for your children's 529 plan or education savings.
- Investment Growth Modeling: Estimate the future value of stock market, bond, or index fund investments at different expected return rates.
- Savings Account Optimization: Compare high-yield savings accounts by calculating how different interest rates and compounding frequencies affect your balance.
- Emergency Fund Building: Plan regular monthly deposits to reach your target emergency fund amount and see how interest accelerates the process.
- Debt vs. Investment Comparison: Compare the cost of debt interest against potential investment returns to decide whether to pay down debt or invest.
- Financial Independence: Model your path to financial independence by projecting when your investment portfolio reaches your target passive income level.
- Teaching Financial Literacy: Demonstrate the power of compound interest to students with visual charts and year-by-year growth breakdowns.
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which only earns on the original amount, compound interest creates exponential growth -- often called "interest on interest" -- making it one of the most powerful concepts in finance.
Does compounding frequency matter?
At the same positive nominal annual rate, higher compounding frequency changes the result. For $10,000 at 5% over 10 years without contributions, this formula gives $16,288.95 annually and $16,486.65 daily, a difference of $197.70.
How do additional contributions affect compound growth?
Regular contributions dramatically accelerate compound growth because each new deposit also begins earning compound interest. Even small monthly contributions can make a massive difference over long time horizons due to the compounding effect.
What interest rate should I use for stock market investments?
Use the input as a hypothetical constant-rate scenario. Compare lower, central and higher assumptions rather than treating one historical average as a forecast. Actual investment returns can vary, and taxes, fees and inflation are not included.
Tips & Best Practices
- Start early: The single most powerful factor in compound growth is time. Starting 10 years earlier can often double your final amount even with smaller contributions.
- Be consistent with contributions: Regular monthly contributions take advantage of dollar-cost averaging and maximize the compounding effect over time.
- Use conservative estimates: For long-term planning, use a slightly lower interest rate than historical averages to build in a margin of safety for your financial goals.
- Compare compounding frequencies: Run the calculator with different compounding options to see how daily versus monthly or annual compounding affects your results.
- Export and track progress: Download your growth projections as CSV and update them annually to track how your actual investment performance compares to projections.
- Account for inflation: Inflation is not included. For an annual effective return and an annual inflation rate, real return is (1 + return) / (1 + inflation) − 1. Subtracting the rates is an approximation.