Greyes and North 56 - Shirts.
Arm pit to Arm pit measurement in centimeters | Measurements are accurate to within 1 - 2 centimeters*
How to Ensure you order the right size
The easiest way is to take an existing shirt that fits you well, lay it flat and measure across the chest from armpit to armpit.
This give you the half chest measurement once you have this, check the size chart and order the size closest to what you measured on your existing shirt.