Compound interest calculator with monthly contributions
This compound interest calculator with monthly contributions shows how your savings could grow by combining an initial investment, recurring contributions and time.
Your inputs are processed in your browserInvestment details
Contributions are added at the end of each compounding period. Monthly is selected by default.
Simulation result
Return on contributions
Annual breakdown
| Year | Contributions | Interest | Final balance |
|---|
How compound interest works
Compound interest adds the interest earned to your balance, so that balance can generate more interest in later periods. This is why time and consistent contributions can have a meaningful effect.
With contributions at the end of each period, the formula is A = P × (1 + r/n)^(n×t) + C × (((1 + r/n)^(n×t) − 1) / (r/n)). At 0% interest, the result is simply the initial investment plus all contributions.
How to read the result
Total contributed adds the initial investment and all recurring contributions. Interest earned is the part of the final balance that comes from the simulated growth, not from your contributions.
The annual table shows how the balance changes and how much interest is generated each year. Change the frequency to compare the effect of adding interest more or less often.
Assumptions and reference
The simulation uses a constant nominal rate and contributions at the end of each period. It does not forecast an actual investment or account for inflation, taxes, fees or changing returns.
For an educational reference, see the Investor.gov compound interest calculator. Reviewed on August 5, 2026.
Frequently asked questions
What does this compound interest calculator calculate?
It calculates the final balance, total contributions and interest earned from the initial investment, recurring contributions, annual rate, term and selected frequency.
What does compounding frequency mean?
Frequency is how many times per year interest is applied and added to the balance. Contributions are made at the end of each selected period; monthly is the most common option.
Are recurring contributions included?
Yes. You can enter a recurring contribution; the tool adds it at the end of each period and shows its effect on the final balance.
Are my details sent to a server?
The calculation runs in your browser, and the details you enter are not sent to the tool's server.