Bella+Canvas sizes

Code	Size name	Chest to fit
XS	Extra Small	31"–34"
S	Small	34"–37"
M	Medium	38"–41"
L	Large	42"–45"
XL	Extra Large	46"–49"
2XL	Double Extra Large	50"–53"
3XL	Triple Extra Large	54"–57"

Taken from Bella+Canvas Unisex Fit & Size Chart.