Measuring arm holes?

How-to Questions
1

i’m working on my tilted duster and this is the first time i’ve ever knit a sweater that involves seaming. (i always did top downs)
anyway, I am knitting the back piece of this sweater, and i’ve just finished putting in the decreases for the arm holes. it now says to knit until the arm holes measure 8.5 inches…

uhh…
so do i
A-measure them on the diagonal from where i started the decreases to the top of where i’m knitting now?
B-measure them on the diagonal from where i finished the decreases to the top of where i’m knitting now?
C- measure with a tape measure along the curve of the arm hole from where i started the decreases to the top of where i’m knitting more?

i know that this measurement is somewhat important because it’ll mean either a nice fitting sweater or something too tight or too baggy.

thanks a bundle for your help!!!

2

Measure straight up. Lay a ruler or magazine or something straight across the back at the place where you bound off for the armhole and measure straight up from that.

3

thank you, ingrid. you are very wise! :notworthy:

4

Here again is a place where standardizing terminology could help many new and intermediate knitters; I am among the latter.

In my mind,

“armhole measurement” = measurement of the circumference of the armhole from top of shoulder all the way around the opening and returning to the top of the shoulder.

“armhole DEPTH” = the straight line distance between the top of the shoulder and the lowest point of the armhole opening.

Wouldn’t it be great if people always wrote either “armhole circumference” or “armhole depth”?