How to use
- Enter the starting amount, rate and years.
- Add monthly contributions and choose the compounding frequency.
- Read the yearly table and chart.
Worked example
$10,000 at 5% compounded annually for 10 years grows to $16,288.95.
Supported formats and limits
| Input | Principal, rate, years, contributions, compounding |
|---|---|
| Output | Final balance, interest earned, yearly table, chart |
| Engine | Period-by-period simulation (handles contribution timing exactly) |
Limitations
- Returns are shown as a constant rate; real investments vary year to year and can lose value.
- Taxes and account fees are not deducted.
Questions
How is compounding modeled?
Interest is credited at the end of each compounding period (annually, semiannually, quarterly, monthly or daily) and balances are kept at full precision, rounded to cents only for display. This matches P(1 + r/m)^(mt): $10,000 at 5% compounded annually for 10 years grows to $16,288.95.
Does deposit timing matter?
Yes. Deposits can be made at the start or the end of each weekly, two-weekly, monthly, quarterly or yearly period. A deposit at the end of a period earns no interest for that period, so start-of-period deposits end slightly higher.
What does the inflation figure mean?
If you enter an inflation rate, the final amount is also shown in today's money: the balance divided by (1 + inflation) to the power of the years.
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