For Chest - Measure 1" inch below armhole, from seam to seam across chest. For Length - Measure from shoulder to bottom of shirt.
Small - Chest 20" - Length 27"
Medium - Chest 22" - Length 28"
Large - Chest 24" - Length 29"
XL - Chest 26" - Length 30"
2XL - Chest 28" - Length 31"
3XL - Chest 30" - Length 32"