X Small- Measurements are Neck 13-1/2" Chest   19-1/2" Tapers to about 18" by the waist.

Small-  Measurements are Neck 14-1/2" Chest   21-1/2" Tapers to about 20" by the waist.

Medium-  Measurements are Neck 15-1/2" Chest  22-1/2" Tapers to about 21" by the waist.

Large-  Measurements are Neck 16-1/2" Chest  23-1/2" Tapers to about 22" by the waist.

X Large-  Measurements are Neck 17-1/2" Chest 24-1/2" Tapers to about 23" by the waist.

XX Large Measurements are Neck 18-1/2" Chest   25-1/2" Tapers to about 24" by the waist.

3X Large Measurements are Neck 19-1/2" Chest   26-1/2" Tapers to about 25" by the waist.

Measure your favorite buttondown collar shirt and order what compares the best.  Chest and
waist measurements are taken with the shirt layed flat from seam to seam.
Every manufacturer
is different, but if you have any Slimfit Ben Shermans or Buttondown shirts from the Merc,
order the same size in these and they should fit great!