If you're getting customer reviews on your XL shirts saying "the chest fits but the shoulders drop," or "I can't move my arms," your sizing specifications have a pattern grading curve error. Linear grading curves do not work across a wide size spectrum.
1. Why Linear Sizing Fails
Standard linear grading assumes that a human body scales by the exact same increments as it grows. For instance, if you add 1 inch to the chest circumference from Small to Medium, you simply add 1 inch from Large to XL, and another to 2XL.
However, human shape changes non-linearly. Shoulder slopes, neck openings, and upper arm widths scale at different rates than chest widths.
2. Inclusive Plus-Size Grading (2XL-4XL)
Plus sizes require a separate grading block. Circumference measurements must leap by 2 inches to 2.5 inches rather than 1 inch to accommodate bust and arm ease. Neck widths should not scale linearly, or else collars will hang too loose.