Investment Calculator – Compound Interest & Monthly Contributions
Use this free investment calculator to estimate long-term growth with compound interest. Add an initial amount, monthly contributions, interest rate, and time period to see how your investment may grow year by year.
Investment Calculator
Instantly see how your investment can grow with compound interest and monthly contributions.
Final value:
Total contributed:
Total interest earned:
| Year | End balance |
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How to use the Investment Calculator
Use this investment calculator to estimate how your money can grow over time with compound interest and monthly contributions.
Choose your currency (USD, EUR, GBP, or NOK).
Enter your initial investment.
Add your monthly contribution.
Set an annual interest rate.
Choose how many years you plan to invest.
Results update instantly as you change values.
You’ll immediately see:
Your final investment value
How much you contributed
How much growth comes from interest
A clear year-by-year breakdown
What do the results show?
Final value
The total estimated value of your investment at the end of the selected period.Total contributed
The total amount of money you actually put in (initial + monthly contributions).Total interest earned
The difference between your final value and the money you invested — this is your growth from compound interest.
The yearly table shows how your balance increases at the end of each year.
What-if scenarios
Use the quick buttons to explore different outcomes:
+1% return – see how a slightly higher return impacts growth
+50 / month – test the effect of saving a bit more each month
+5 years – understand the power of staying invested longer
Small changes can make a big difference over time.
Export and sharing
You can easily save or share your results:
Download Excel (CSV)
Export the yearly results to a spreadsheet for further analysis.Download PDF
Save a clean PDF snapshot of your inputs and results.Copy link
Share a direct link with your current values included.
No account or sign-up is required.
Is this calculator accurate?
This tool uses standard compound interest calculations with monthly compounding. Results are estimates based on the values you enter.
Actual investment returns can vary due to:
Market performance
Fees and taxes
Changes in contribution amounts
Timing of investments
Use this calculator for planning and comparison, not as financial advice.
Who is this calculator for?
Long-term investors planning steady monthly contributions
Beginners learning how compound interest works
Anyone comparing different savings or investment strategies
Students, educators, and personal finance learners
The calculator is designed to be fast, simple, and easy to understand on both desktop and mobile.
Why use an online investment calculator?
Compound interest rewards time and consistency. Seeing real numbers makes it easier to:
Stay motivated
Set realistic goals
Understand how small changes affect long-term results
This tool helps turn abstract percentages into clear, practical insight.
Can I use different contribution amounts over time?
This calculator assumes a fixed monthly contribution for simplicity. If your contributions change over time, you can run multiple scenarios or use the what-if buttons to estimate the impact of higher or lower savings.
Does the calculator account for inflation?
No. All results are shown in nominal values. Inflation is not deducted automatically. If you want a more conservative estimate, you can lower the interest rate to approximate inflation-adjusted returns.
When are monthly contributions added?
Monthly contributions are added at the end of each month. This is a common and conservative assumption used in many investment calculations.
What compounding frequency is used?
The calculator uses monthly compounding. This reflects how most long-term investments grow when returns are reinvested regularly.
Can I use this calculator for retirement planning?
Yes, the calculator is suitable for basic retirement planning and long-term projections. However, it does not include taxes, fees, or withdrawals, so it should be used as a planning aid rather than a complete retirement model.
Why does a small change in interest rate matter so much?
Because of compound interest. Over long periods, even a 1% difference in annual return can significantly increase or decrease your final balance. This is why time and consistency are often more important than short-term performance.
Are fees and taxes included?
No. Investment fees, taxes, and account-specific costs are not included. If your investments have fees, you can subtract them from the interest rate to get a more realistic estimate.
Is my data saved or tracked?
No. All calculations run entirely in your browser. No inputs or results are stored, tracked, or sent to a server.
Why don’t the results match my bank or broker exactly?
Different platforms may use:
Different compounding assumptions
Different contribution timing
Fees or taxes behind the scenes
Small differences are normal when comparing estimates from different tools.
Can I rely on this calculator for financial decisions?
This calculator is intended for educational and planning purposes only. It helps you explore scenarios and understand growth patterns, but it does not replace professional financial advice.
About the Investment Calculator
The Investment Calculator is a simple and lightweight tool designed to help you estimate how your money may grow over time. Instead of dealing with complex spreadsheets or financial jargon, you can quickly explore realistic investment scenarios directly in your browser — anytime, on desktop or mobile.
By combining an initial investment with regular monthly contributions and compound interest, the calculator gives you a clear picture of long-term growth and the impact of consistency.
How it works
The calculator uses standard compound interest formulas with monthly compounding. Each month, interest is applied to your current balance, and your contribution is added at the end of the month. Over time, this creates a compounding effect where both your contributions and previous gains work together to grow your investment.
All calculations are performed locally in your browser. No data is sent to a server, and no account is required.
Why trust the results?
The calculations are based on well-established financial formulas commonly used in personal finance planning and investment projections. While real-world investments can fluctuate, this model provides a clear and consistent way to compare scenarios and understand long-term trends.
Because the tool runs entirely in your browser:
Your inputs are private
Results are instant
The calculator behaves the same across devices and sessions
Designed for real use
Instant feedback: results update immediately as you change values.
What-if scenarios: quickly test higher returns, longer time horizons, or increased monthly savings.
Clear breakdown: see how much comes from your own contributions versus growth.
Export options: download your results as Excel (CSV) or PDF for later reference.
Mobile-friendly: works smoothly on phones, tablets, and desktops.
No account or setup: open the page and start calculating.
Who is it for?
Long-term investors exploring different savings strategies
Beginners learning how compound interest works
Anyone comparing monthly contributions versus time invested
Students, educators, and personal finance learners
People planning future goals like retirement, large purchases, or financial independence
This investment calculator is intended for educational and planning purposes only. It helps you explore scenarios and understand growth patterns, but it does not replace professional financial advice.
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