What is the half chest size?

All sizing is in centimeters (cm) and represents the half chest measurement, from armpit to armpit, across the garment when laid flat. To check a size, the best thing to do is find a similar garment (T-Shirt, Polo or Hoodie etc) that fits you well, lie it down flat and measure it from side to side. Then match up the measurement to the size guide given for the garment. Note some styles are more fitted than others.