I’m designing a bed frame and using inches as mattresses are in inches (otherwise, yes, I’d be using centimeters) and one of my measurements is 25 1/3". Every time I try to put that into SketchUp using the tape measure tool, however, it ends up as 25 43/64", which I assume is SketchUp trying to make it work with a base-2 system?

@DonutJuice I’m guessing you are a native metric user. There is no 1/3 of in inch in the bizarre archaic imperial fractional system we use, it’s all base 12 and base 2. Sketchup will accept decimalized inches so you can use .33" to get a third. Before you say it, no it’s not exact.

Again, here is no such thing as 1/3 of an inch. Wherever you got the measurement 25 1/3" is wrong, it sounds like someone converted what was a metric measurement for the mattress into inches incorrectly. .33 is not “really” a third either, it’s just pretty close. Thats one of the advantages of a 12 based system like feet… 4 inches is exactly a third. FYI you can switch units on your drawing anytime, to work in the one you are used to and output in another later.

It should be 25 2/3" sorry, (77/3). I guess I’m just worried where the plywood and whatnot I’m dealing with it 0.75", 1.9cm seems a little more obtuse.

I’m confused by this question. There is no measurement in inches with 3 in the denominator, not 1/3 not 2/3 not 77/3.
.75" is 3/4" ply and a very common material.

Sorry, what I’m saying is I have 77" to work with. I want to divide it into three strips. That gives me 25 2/3" in each strip and I wanted to plan that out.

Just napkin math. I have 80" plywood, with four 0.75" separators on it, leaving me with 77" of material to work with, which I’m dividing into three sections, which is 25 2/3" each. I wanted to map that out with SketchUp.