# Calculating Portfolio Visualizer's CASHX Risk-Free Return Benchmark

I would like to understand how to calculate Portfolio Visualizer's CASHX symbol for every month. This ticker is used as a risk-free rate, based on historical 3-month treasury bill rates published by FRED.

According to PV, FRED data must be converted from discount basis to add-on basis by taking the end-of-month discount rate and converting it to add-on rate.

Here are some FRED Data and their corresponding risk-free return rate

Date          FRED      CASHX
1985/01/31    8.05      0.66%
1985/02/28    8.50      0.68%

2020/02/31    1.25      0.13%
2020/03/31    0.11      0.10%