Help measuring armhole?

Still working on my first sweater and first back:

How do I measure the length of the armhole? I did some Dec. and can see the shape changing but now the instructions say to “work even until armhole measures 6.5”, but I don’t know if I can tell where to start my measurements from accurately. Any advice would be sooooo appreciated!!! :??



Put the end of a straight edge at the point where you did the first decrease for the armhole and have it lie horizontally across the back of the sweater. Then use a ruler to measure vertically to the needles.

Thanks Ingrid!
Boy do I feel stupid-that was kind of a no brainer, huh?
I guess I am very doubtful of my abilities so I don’t think of simple solutions like the straight edge.

Thanks again, I’m sure you’ll be hearing from again soon as I tackle the fronts and arms!