Eye balling to me is relying on the numbers that I have repeated over and over. I believe I have stated before most of what we do is not rocket science. 12x15x8,12x15x10,12x15 x12,etc... How much furniture to move etc... P I A Factor. Repetition tends to promote confidence. I truly can't remember the last time I used a tape measure. Except for measuring wheel for property walls