i guess it depends on how you actually measure them. in my 40 years as a machine repairman and in on stint i worked in the shops apint line and i had to maintain maybe 4 sets of belted machines, all fans a few for the chain drive. and in my time on that job i measured then the same way i measured these on the snowblower. by the back of the belt. i laid a tape on a flat surface marked the belt around and ran it own the tape. worked every time. and i do not know about your setup but i have never had a setup that did not have some amount of takeup do to the variances in the mfg. of the belt.
in fact when you have to roder belts in multiple those show be all mace from the same core so that theya re all the same length. if you were to just order lets say 3 belts for a multiple setup one at a time your going to see them at different lengths, and in that situation you can't just take up one as the complete frive gets adjusted all at once. and even then if you were to notice you may even see one that is a bit loose. happens all the time. that is one reason mfg. put at least 3 belts on a multiple drive setup just for that, the engineer knows one belt is going to be a bit loose
what i'm talking about here is that i did order the impeller belt from huskvarna,poulan and sears, under the part number in the book and they all showed up for the drive section. that is why i asked. if anyone happen to order or have one on hand that fits and what the number were or if they new the size. i could not use mine as it was a old spare form some other intem that i had laying around. could have been from a car, a machine, a lawn mower or whatever!
in all my research i did finally find a company that was able to cross the number and gave me the one size i had at 38.2 for the drive and 36.4 for the impeller. so i passed that on here for other that happen to need to source one form a local part store, as most online are out, hey it is winter.
so you really do not need the so called belt measuring tool if you just lay them flat on a surface and run them along a tape from the ene of the tape to the mark you placed on the belt as you started. that actually is how they are intended to be measured. thanks bp