Online Tool Store
Compound Interest Calculator
Calculate compound interest, future value, and recurring deposits for free. Explore long-term growth privately in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Future value
Contributions
Interest earned
How compound interest is calculated
- Enter the initial balance, annual rate, period, and compounding frequency.
- Add an optional monthly contribution to model regular saving.
- Compare total contributions with projected interest and future value.
The starting principal uses A = P(1 + r/n)nt, where P is principal, r is the annual decimal rate, n is compounds per year, and t is years. Monthly deposits use the future-value-of-an-annuity formula PMT × ((1 + r/12)12t − 1) ÷ (r/12). The two future values are added, while interest earned is the result minus principal and deposits.
This estimate assumes a constant rate and deposits at the end of each month; taxes, fees, inflation, and investment risk are not included.
FAQ
What is compound interest?
Compound interest is growth calculated on both the original principal and interest accumulated in earlier periods, so the balance can grow faster over time.
How are monthly contributions handled?
The calculator assumes each contribution is deposited at the end of the month and compounds monthly at the entered annual rate.
Does compounding frequency affect recurring deposits?
The selected frequency applies to the starting principal. Monthly contributions use a monthly rate because they are modeled as end-of-month deposits.
Does this include taxes, fees, or changing rates?
No. It is an illustrative projection using a constant rate. Actual returns can vary, and taxes, fees, inflation, and market changes are not included.
Are my financial figures stored or uploaded?
No. The calculation runs entirely in your browser, and the values you enter are not uploaded to Online Tool Store.
How we compare
| Feature | Online Tool Store | Investor.gov | Calculator.net |
|---|---|---|---|
| Recurring monthly deposits | Included | Included | Included |
| Currency display choices | Seven currencies | Generic currency values | Generic currency values |
| Account or installation | Neither required | Neither required | Neither required |
Investor.gov is a strong choice for US investor education, while Calculator.net offers broader supporting calculations. Choose Online Tool Store for a focused, private projection with recurring deposits and convenient currency formatting.