Heres how I do this!
I sell a little, and have learnt this from the masta....
If you can pick it up in one hand from the end, then it don't need splitting as a general guide.
Then I start finding out what stoves are out there. Hazel has a pretty good sized box, and can fit fairly decent pieces in there. Here at the house I have a insert that is happier with small stuff, 3-4 inches is about right. My ol' man has the same stove I use at the shop, and they can fit large stuff. 6 in, or bigger. Ann never complained, so she must have a decent stove as the usual size is what I deliver there (5 in). Richard on the other hand has some kind of overgorwn blast furnace that can literally burn 12" LOGS!!! Then Frank needs the smaller stuff....
I have to split accordingly to where it is going. I find that if your length is a little long then splitting it a little smaller is helpful.
-Pat