About the Compound Interest Calculator
Small differences in rate, frequency and time add up dramatically. Set an opening balance, a regular contribution and a rate to see the future value, the interest earned and a year-by-year chart of the balance.
How to use it
- 1Set the starting balanceEnter what you have today, or zero to model contributions only.
- 2Add contributions and rateChoose monthly or annual deposits, the annual rate and the compounding frequency.
- 3Review the projectionThe table separates contributions from interest so you can see when compounding takes over.
Why use this compound interest calculator?
- Nothing leaves your device. The work happens in your browser tab. There is no upload endpoint in this app, so your files and text cannot be stored, logged or seen by us.
- No upload wait. You skip the round trip to a server entirely. Results are limited by your own CPU, not by network speed or queue size.
- Free, no account, no quotas. No sign-up wall, no watermark, no daily limit. Optional accounts only exist to save favourites and presets across devices.
Frequently asked questions
Is my projection safe to use here?
Yes. This tool runs entirely in your browser using JavaScript. Nothing you paste or open is sent to a server, and the page keeps no copy after you close it.
Do I need to create an account?
No. Every tool is fully usable without signing in. An account only adds saved favourites and reusable presets.
Does it work on a phone?
Yes. The interface is mobile-first with large touch targets and a stacked layout, so it works on phones and tablets as well as desktops.
What is the compound interest formula?
For a lump sum: A = P(1 + r/n)^(nt), where P is principal, r the annual rate as a decimal, n the compounds per year and t the years. Regular contributions are added with an annuity formula.
Is the result adjusted for inflation?
No. The projection is in nominal currency. To see real purchasing power, subtract expected inflation from the interest rate before calculating.