Always measure twice before cutting. But then, cut as many times as you need to till you get it right.
“Measure twice, cut once” is right up there with “You can never have enough clamps.” The reason is simple: Double check your measurement before committing to forever changing the size of a piece of wood.
And while I’m pretty good at measuring and generally have no problems with cut lists, I do tend to be slightly off whenever measuring between two points. That is, measuring the exact distance between two surfaces in order to cut something that will then fit perfectly between them.
A rigid rule doesn’t fit between two points shorter than itself, so you have to lay that rule across the gap. When I do this, I invariably angle the rule just slightly, throwing my measurement off. Not much, but sometimes enough to ruin the cut. Likewise, a tape measure can’t get a 100-percent accurate inside measurement either. A perfect example of both of these is cutting baseboards or other molding that must fit between two fixed points.
My solution? Go ahead and measure twice for the same reason you always do – to make sure your cut mark is as accurate as can be. Then cut just a hair wide of the mark and test fit. If your piece is too big – and it will be – it’s an easy task to shave off a tiny bit more to sneak up on the exact cut.
A waste of extra time and effort? Depends on how you look at it. Cutting twice, in my humble opinion, takes a lot less time that cutting incorrectly once… and having to start over with a whole new workpiece.