Compound Interest Calculator
Enter a starting amount, interest rate, compounding frequency, and optional regular contributions to see exactly how your investment grows year by year — a clear picture of compounding's long-term effect.
All calculations happen on your device — no financial figures are sent to a server.
For informational purposes only — not financial advice or a guarantee of actual investment returns.
What this tool does
Projects how an amount grows with compound interest over years, with an optional monthly contribution, separating what you put in from what the return added, plus a year-by-year growth chart.
When to use it
- Seeing what regular saving does over the long term.
- Comparing starting now against starting a few years later.
- Estimating what an amount becomes after a period at an assumed rate.
- Understanding the difference between simple and compound interest in practice.
How to use it
- Enter the "Initial amount".
- Enter the "Expected annual return %" and "Investment term (years)".
- Enter a "Monthly contribution" if you will add regularly.
- Click "Calculate growth" and read the final balance, total contributions and total return.
A practical example
Input
An initial amount with a monthly contribution at an annual rate over 20 years.
Output
The final balance, what you actually paid in, and the total return — the gap between those two figures is what compounding produced.
The yearly chart shows the property that matters most: growth is slow in the early years and then accelerates, because the return starts generating returns of its own.
Limitations
- This is for information only and is not financial advice or a guarantee of any actual investment return.
- The assumed rate is constant, while real returns rise and fall — a bad year early on hurts more than an average suggests.
- It excludes inflation, taxes and management fees, all of which reduce the real return.
- The term must be greater than zero.
Privacy and processing
Your starting amount, contributions and assumed rate are projected on your device and never sent anywhere.
Technical notes
- Monthly contributions are applied through the term, so each one compounds according to how long it has been invested.