It's a rule of thumb, take it with a grain of salt.
I need to hire a teenager to help me with my paperwork...
Let's see... 7/27/2013 ... Giant's game, half-frame
Dektol 1:9 on fresh Tri-X 400 TX 135-36 12/2014 batch 1781
5 minutes 68-degrees F
Aim CI 0.4 - 0.5
Actual CI possibly 0.4 - 0.5 but didn't do sensitometry.
(I deliberately under-developed to aim to a Grade 3 paper instead of Grade 2, long story but I was going for maximum grain).
p.s. The photo is a flat-bed scan of a print. I mention that because so many grain examples are negative scans. Negative scanning can cause exaggeration or misrepresentation of actual grain. This is the grain on a print.