(27S) Interest Rate Conversions

[Dave Britten]

This program replicates the nominal/effective interest rate conversions from the 17BII, 19BII, etc. It's implemented as two equations, one for periodic compounding, and one for continuous compounding. Both use the LNP1 and EXPM1 functions to provide accurate results for very large numbers of compounding periods, or very small interest rates.

Periodic compounding

Code:

I%CONV.PER:EFF%=EXPM1(LNP1(NOM%÷100÷P/YR)×P/YR)×100

Continuous compounding

Code:

I%CONV.CONT:EFF%=EXPM1(NOM%÷100)*100

Example:

Convert a nominal rate of 4.75% compounded monthly to an equivalent nominal rate with quarterly compounding.

Select the I%CONV.PER equation, press [CALC].

4.75 [NOM%]
12 [P/YR]
[EFF%] Output: 4.85
4 [P/YR]
[NOM%] Final result: 4.77