^^^This^^^ I've not measured/marked a stick of firewood in over 30 years.after cutting a few cords you can usually guess with in a 1/2" give or take...its like riding a bike or tying your shoe, it gets done automatically by repetition.
I guarantee one thing. If you rely on a tree removal company to cut your logs to firewood length, almost nothing will be cut the right length and almost nothing will be cut square. Angled cuts will be everywhere and your log splitter will let you know.