Using the Interest Calculator
To examine interest on a single deposit, use zero for the monthly contribution. To model an account with recurring saving, add the regular deposit and keep the timing assumption in mind: deposits arrive after that month’s growth.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Starting balance
- 10000
- Monthly contribution
- 200
- Annual nominal return (%)
- 5
- Years
- 10
Example result
- Future balance
- 47,526.55
- Total contributions
- 34,000
- Growth
- 13,526.55
Method and assumptions
Monthly compounding with end-of-month contributions and a constant nominal annual rate. Taxes, fees and market fluctuations are excluded.
Separate contributions from growth
An ending balance can grow because you put more money in, because the assumed return is higher, or because the money has more time to compound. Those are different effects. Keep the contribution schedule consistent when comparing rates, and distinguish a mathematical projection from a return that is contractually guaranteed. Fees and taxes need their own assumptions.
Common question
Why does interest increase faster over a longer period?
With compounding, previously earned interest becomes part of the balance earning future interest. That effect grows with time, provided the interest remains in the account.
Guide updated .