I have a Matson combination scale ruler; bought it 25 years or so ago. It is sturdy, flexible, and well printed; super handy for so many projects. One side even has some helpful additional information such as drill sizes, etc. I like it. However, it falls short in one vital function - there are no inches. Lots of scale feet, but translating HO feet to inches requires two rules. Kind of a pain in the rear when converting HO to inches or inches to HO (and possibly other scales). Is there available a 12 rule with HO scale feet along one edge and inches along the opposite edge? Nothing else; just the HO feet and inches. Lordy, I'd love to have one. (And one in N scale if I decide to go that direction next year)
There may be one available, but I'm not aware of it. I have the same scale ruler as yours and have had it about the same amount of time and encountered the same 'problem' as you mention. My solution was to open the calculator in the 'applications' program and make a table, (inWordPad) of the conversions you seek. That way I can keep the page open for reference while working. And, of course you could print it out if you want.
Look here. You'll have to print it out. I printed one for N scale and mounted it on cardstock. Works great.