This gem implements some useful Excel formulas like PMT, IPMT, NPER, PV, etc...

The finance library provides a Ruby interface for working with interest rates, mortgage amortization, and cashflows (NPV, IRR, etc.).

A ruby port of numpy-financial functions. This library provides a Ruby interface for working with interest rates, mortgage amortization, and cashflows and other stuff from finance.

Implementation of Loan/Mortgage functions in Ruby language. APR function and PMT function. In calculations it includes implementation of bank fee, marketplace fee, fees for each payment to provide the most precise calculation at very high speed.

The finrb library (forked from the finance gem) provides a Ruby interface for financial calculations/modeling. Working with interest rates, Mortgage amortization, Cashflows (NPV, IRR, etc.) and other basic utilities.