TOOLOG / WEB UTILITY
Compound Interest Calculator | Monthly Contributions & Future Value
Calculate future value, contributed principal, investment gain, and inflation-adjusted value from an initial investment, month-end deposits, annual return, term, and compounding frequency.
Try the tool
Enter your details below. Results update instantly.
Enter an initial amount or monthly contribution, return, and term.
Assumes month-end contributions and converts the selected nominal compounding rate to an equivalent monthly rate. Taxes, fees, and return volatility are excluded.
Why use a compound interest calculator?
When planning investments, common questions are:
- How much will this become in 10 years?
- What changes if I add money every month?
- What is the real value after inflation?
This tool answers those with quick numbers.
Key features
- Monthly investment planning: combine an initial investment with recurring month-end contributions
- Compounding comparison: switch among monthly, quarterly, semiannual, and annual compounding
- Inflation-adjusted value: discount the ending balance by an optional annual inflation rate
- Responsive results: review ending balance, contributed principal, gain, and real value on desktop or mobile
- Clear validation: distinguish missing inputs, out-of-range values, oversized results, and copy failures
- Explicit assumptions: see the deposit timing, rate conversion, and excluded costs used by the estimate
How to use
- Enter initial investment, monthly contribution, annual return, and term.
- Choose compounding frequency.
- (Optional) Enter inflation rate to view real-value estimate.
- Review the ending balance, total contributions, estimated gain, and inflation-adjusted value. Use Fill sample values to test the flow or Copy results to share the summary.
Monthly contributions are treated as month-end deposits, using a monthly-equivalent rate derived from the selected nominal compounding frequency. Taxes, fees, and return volatility are not included.
Example
For an initial investment of KRW 1,000,000, monthly contributions of KRW 300,000, a 7% annual return, a 10-year term, monthly compounding, and 2.5% inflation, the calculator shows:
- Estimated ending balance
- Total principal contributed
- Estimated investment gain
- Inflation-adjusted ending value
Use the example to compare a 0% return or a different compounding frequency without changing the underlying month-end contribution assumption.
Empty and error states
The calculator waits until an initial investment or monthly contribution, annual return, and whole-number term are valid. Each field has its own range message, results remain blank after invalid input, and Copy results stays disabled until a valid estimate exists. Clear removes all entries and returns compounding to monthly. If the browser blocks clipboard access, the status area reports the copy failure.
Related tools
- Repayment comparison: Loan Calculator
- Percentage math: Percent Calculator
- Savings check: Discount Calculator
FAQ
When is each monthly contribution added?
The calculator assumes month-end deposits and derives an equivalent monthly rate from the selected monthly, quarterly, semiannual, or annual compounding frequency.
Can I use a 0% annual return?
Yes. This boundary case shows the contributed principal without investment gain and helps verify your deposit plan.
How is the inflation-adjusted value calculated?
The calculator discounts the estimated ending balance to present value using the annual inflation rate entered. Leave inflation blank if you only need the nominal ending balance.
Why does compounding frequency affect the estimate?
The selected nominal annual return is converted to an equivalent monthly rate. Monthly, quarterly, semiannual, and annual compounding therefore produce different effective annual returns even when the displayed nominal rate is the same.
Is this a guaranteed investment forecast?
No. It is a fixed-return planning estimate and excludes taxes, fees, and market volatility.
Summary
Use this compound interest calculator to compare recurring investment plans by ending balance, contributed principal, estimated gain, and inflation-adjusted value under clearly stated assumptions.