Length (A): Measured from the highest point of the shoulder to the lowest bottom part of shirt. Width (B): Measured 1" below armpit, edge to edge.
These measurements are the actual garment size when laid down flat. If you are not sure which is the best size is for you, lay one of your comfortable fitting t-shirts flat and measure it using the guide above.
All cotton is prone to shrinkage after first wash (even pre-shrunk cotton). Expect 1/4” - 1/2” of shrinkage on the measurements listed above after your first wash.