Compound Interest Calculator
Enter a starting balance, an annual interest rate, the number of years, and an optional monthly contribution. The calculator simulates each compounding period (annual, quarterly, monthly, or daily) and shows the final balance, total contributed, and total interest earned — plus a year-by-year schedule with a bar showing how the balance grows over time.
Yearly schedule
| Year | Balance | Interest | |
|---|---|---|---|
| 1 | $11,740 | +$540 | |
| 2 | $13,568 | +$629 | |
| 3 | $15,490 | +$722 | |
| 4 | $17,510 | +$820 | |
| 5 | $19,634 | +$924 | |
| 6 | $21,867 | +$1,032 | |
| 7 | $24,213 | +$1,147 | |
| 8 | $26,680 | +$1,267 | |
| 9 | $29,273 | +$1,393 | |
| 10 | $31,998 | +$1,526 |
How to use
- Enter the starting balance (principal) and annual interest rate.
- Set the number of years and any monthly contribution.
- Pick the compounding frequency (monthly is the default).
- Read the final balance, interest earned, and yearly schedule.
Frequently asked questions
- Which formula is used?
- Period-by-period compounding: each period, interest = balance × (rate / n), then balance += interest + contribution_per_period. n is the compounding frequency per year.
- Where does the monthly contribution go?
- It's converted to a per-period contribution by 'monthly × 12 / n' so the annual total stays the same regardless of compounding frequency.
- Are taxes and inflation accounted for?
- No. The result is the nominal balance before taxes and before adjusting for inflation. To see real purchasing power, subtract your expected inflation rate from your interest rate before entering.
- Does it work with negative rates?
- Yes — enter a negative rate to model a depreciating balance, like a fund losing value.
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