THE NUMORIX GUIDE
How to use the Compound interest calculator
Last reviewed September 14, 2026
What this calculator does
The converter first turns the input nominal rate into an effective annual rate.
Formula and method
The converter first turns the input nominal rate into an effective annual rate. For a finite compounding frequency m it uses (1 + nominalRate/m)^m - 1; for continuous compounding it uses exp(nominalRate) - 1. It then solves the nominal rate at the requested output frequency that produces the same effective annual rate.
Variables and inputs
Enter the input interest rate as a percent and choose its compounding convention from annually, semiannually, quarterly, monthly, semimonthly, biweekly, weekly, daily, or continuously. Choose a separate output convention. The result includes the equivalent APY and output nominal rate.
Worked example
A nominal 6% rate compounded monthly has periodic rate 0.06 / 12 = 0.005. Its effective annual rate is (1.005)^12 - 1 = 0.0616778, or 6.16778% APY. If the output is annually, the equivalent output rate is the same 6.16778% because one annual compounding period produces that APY.
How to interpret the result
APY is the common comparison point for finite compounding frequencies in this tool. Two products can advertise the same nominal rate but have different effective annual yields if their compounding conventions differ. A continuous result uses a logarithmic conversion rather than a finite period count.
Common mistakes to avoid
Do not divide an APY by 12 and call it a monthly equivalent without converting it. Distinguish nominal APR-style rates from effective annual rates. Keep the input and output frequency labels visible when copying the result into another calculation.
Assumptions and limitations
This route converts rates only; it does not model deposits, withdrawals, fees, taxes, variable rates, or an account's actual day-count rules. It assumes the stated nominal rate is nonnegative and constant for the year.