How to Measure Underarm Depth Accurately

I came up with another method to measure underarm depth accurately. 

The difficulty in getting an true measurement is that you are trying to measure a curve on the body that becomes a straight line on a flat pattern. At the same time it needs to be measured at the outside edge of the shoulder where the sleeve cap meets the armhole. It is difficult to measure on someone else and almost impossible to measure on yourself.

To use this method you need a tank that has straps that go straight up, mine sits right on the bony protrusion at the back of my shoulder that defines where your armhole seam should sit. Avoid tanks with straps that are purposely cut away at the shoulders. Even the straight straps tend to fall in towards the center slightly. You can usually see that they are doing so by the wrinkling that happens just at the underarm. The strap should be at least an inch wide and racer-back styles will not work. The other advantage of a tank is that you can very clearly see where the underarm falls on your body.

Put on your tank and look at it sideways, you can use a one inch ruler held under your arm pit to assess if you have the minimum one inch of ease in the armhole. If you like a greater depth that's fine, the whole point here is to find your personal number for required ease. If it's too deep for you, pin the strap of the tank to pull it up into the correct location. You can see my pin with the yellow glass head in the photo. Take the tank off and lay it flat, my photo shows how you will get the measurement that is appropriate for you. You now have a measurement that you can check on the next pattern you choose to knit. This will help you to assess patterns and make decisions on customizing them for better fit.

I checked two patterns in knitting magazines and looked at garments in my size with set in sleeves. The armhole depth was 1.5 inches too long for me on the first and 2.5 inches  on the second. I am 5' 2", therefore I am not surprised by those numbers. How about you? Do you alter the armhole depth on garments you knit? I wrote about how to do this in a previous post here.