# Finding 3month TBill given daily rates

I am working on updating a database and one of the sections that requires updating is the 3 month T-bill rates for each month of the past ten years. I have the past nine years' data from before, and have been trying to figure out how to get the values that were produced. The website that provides these rates is: https://www.treasury.gov/resource-center/data-chart-center/interest-rates/Pages/TextView.aspx?data=yieldYear&year=2019

However, the 3month rates provided on the treasury website are given daily, whereas I need them to be monthly.

For example (see below...and disregard the crediting rates): the April 2018 3month Tbill rate is .01771487

How can I find the January 2019 3month Tbill rate?

Thanks!

• I went to the treasury.gov page and I took the daily yields of 3mo tbills for April 2018. The average is 1.788095 which is different from your value of 1.771148, so I don't know how this is computed. Do you have any clue the method they use? Commented Jul 8, 2019 at 16:46
• @Lin The St. Louis Fed posts this data. Though, their number for April 2018 is different from yours. They use the average bank discount rate for the given month. For April 2018 that number is 1.757619048. Here is the link if you'd like to check it out. fred.stlouisfed.org/series/TB3MS Commented Jul 8, 2019 at 16:59
• @amdopt Thanks for your response. Just curious though, on the website you provided, where did you find the full "1.757619048"? I see the graph, and when I hover over April 2018 it shows only "1.76" Thanks
– Lin
Commented Jul 8, 2019 at 17:25
• @Lin go here fred.stlouisfed.org/series/DTB3 and download the raw data using the link on the page. You will see that it is just a simple average. Commented Jul 8, 2019 at 17:30
• @amdopt thank you!
– Lin
Commented Jul 8, 2019 at 17:47