by Terry Horlamus
Excerpted from Threads #101, pp. 66-70

The term pattern grading may initially conjure up visions of complicated measurements and fancy rulers, but once the basic concept is understood, the actual process of grading is easy, especially using the method I outline here. This means that you—the home sewer, custom dressmaker, or independent designer—can do just as good a job as Vogue, Burda, Calvin, or Donna.

	Why grade? The purpose of grading is to proportionally increase or decrease the size of a pattern, while maintaining shape, fit, balance, and scale of style details (dress, original design).

I'll explain the thought process behind grading and touch upon the three different methods used in the industry today. Then I'll take you step-by-step through a simple cut-and-spread grading method and provide the measurements and formulas you'll need to get started. So whether you want to take a beloved pattern up (or down) a size or two or you want to create a small line of clothing, pattern grading is an important tool. Once you understand it, you'll be able to take your sewing to the next level.

The basic concept
Historically, the science of grading went hand-in-hand with the advent of commercial patterns and the mass-production of pattern-built clothing some 150 years ago. To properly fit a pattern to a range of sizes, each pattern piece needed to be graded, or systematically increased or decreased. Today, pattern companies and apparel manufacturers take a middle-sized pattern (typically a size 12) and grade it up for larger sizes and grade it down for smaller sizes (see One pattern, three sizes).

	One pattern, three sizes
	A base size 12 pattern (left) can be graded up to a size 16 (center) using the cut-and-spread method, and similarly graded down to a size 6 (right)  by cutting and overlapping along specified cut lines.

Methods of grading
There are three basic methods of grading: cut and spread, pattern shifting, and computer grading. No one method is technically superior and all are equally capable of producing a correct grade.

Cut-and-spread method: The easiest method, which is the basis of the other two methods, is to cut the pattern and spread the pieces by a specific amount to grade up, or overlap them to grade down. No special training or tools are required—just scissors, a pencil, tape, and a ruler that breaks 1 in. down to 1/64.

Pattern shifting: Pattern shifting is the process of increasing the overall dimensions of a pattern by moving it a measured dis-tance up and down and left and right, (using a specially designed ruler) and redrawing the outline, to produce the same results as the cut-and-spread method.