Put in the principal, the annual rate from the product disclosure and how long you expect to hold it. The tool returns gross principal and interest under monthly compounding. Before treating that result as spendable money, check the product's compounding frequency, early-withdrawal terms, fees, tax and whether the principal is protected.
Balance estimator (compounded monthly)
Enter a principal, an annual rate and how many years it sits. It estimates the maturity balance and the interest portion, compounded monthly. Everything is computed in your browser: the numbers you enter are not sent anywhere, and taxes and fees are not included.
Enter a principal, an annual rate and years to estimate, compounded monthly.
How the ending balance is worked out
The tool uses “principal × (1 + annual rate ÷ 12) to the power of (12 × years)”. A change to principal, rate or time changes the ending balance. With the page's illustrative defaults, $10,000 at 4% for five years with monthly compounding ends at about $12,200, including about $2,200 of interest.
Monthly compounding is fixed here so inputs can be compared consistently. A real product may compound daily, quarterly, annually or only at maturity. If its schedule differs, the tool is an approximation.
Treat the calculator output as a gross figure
Two products with the same rate can leave different usable balances. Put at least these four checks beside the result:
- What happens to principal. A bank deposit, money-market fund and another investment product are not the same; principal protection and deposit insurance depend on the institution and rules.
- Access terms. A lock-up, early withdrawal and penalties change the interest you actually keep.
- Institution and custody. The issuer, custodian and regulatory status determine where the risk sits.
- Conversion back to local currency. Spreads, fees and exchange-rate movement can offset part of the dollar interest.
Walk from gross balance to usable money
Start with the gross balance, subtract disclosed product fees and any applicable tax, then consider inflation. If the money will return to local currency, include the spread on the conversions and the exchange-rate movement as separate items. Tax treatment depends on the product and where you live; use the official rules and contract.
To isolate the effect of inflation on purchasing power, use the dollar purchasing-power calculator. To compare ways of holding dollars, see where to park dollars and how the four containers differ. Those pages answer different questions, so the inflation output should not be subtracted from interest as though it were a fee.