Knowledge Library
Pattern Grading Explained: How Garments Scale Across Sizes
What grading actually is
Pattern grading is the process of scaling a base pattern — the sample size — up and down across a full size run. It is often misunderstood as simply making a pattern bigger or smaller, but that is not what happens. Grading applies a set of grade rules: measured increments at specific points on the pattern, distributed to reflect how real bodies change between sizes. A chest does not grow uniformly with a hem; a shoulder grades differently from a waist. Grading is, at its core, applied mathematics — a system of rules rather than an act of drawing.
Grade rules and points of measure
Every graded point on a pattern has a grade rule: the amount it moves in the x and y axes for each size step. These rules derive from the points of measure — the standardised body measurements a size chart defines. A well-constructed size chart states, for each size, the exact measurement at chest, waist, hip, shoulder, sleeve length, and so on. The grade rules translate those measurement increments into pattern movement. Because the rules compound across the run, a small error in one rule multiplies with every size, which is why a mis-graded pattern can fit the sample size perfectly and fit no one else.
Why grading by hand drifts
Traditional grading was done by hand or by nesting patterns visually, and both methods are vulnerable to drift. When a grader eyeballs increments or stacks patterns by eye, small inconsistencies accumulate across the size run until the largest and smallest sizes no longer reflect real bodies. This is not a failure of skill so much as a limitation of manual method: the mathematics is exacting, and the human eye is not. The consequence shows up as poor fit at the ends of the range — exactly where a brand can least afford returns.
Why grading should be computed
Because grading is mathematics, it is best computed from a single block applying explicit grade rules. Computed grading keeps every size true to the size chart, eliminates drift, and produces consistent output across the full run in the AAMA format factories expect. It also makes the grade auditable: every point's movement is a stated rule, not a judgement, so errors are visible and correctable. Lyons Intel grades the full size run mathematically from one base block, applying grade rules directly rather than nesting by eye — the same way a senior grader would work, without the manual drift.
Getting grading right commercially
Fit is one of the largest drivers of returns in fashion, and returns destroy margin. Correct grading is therefore not a technical nicety but a commercial necessity: a garment that fits across its full range sells through and comes back less. Brands should define their size chart deliberately, base it on their actual customer rather than a generic standard, and hold their grade rules consistent across styles so a customer who fits one garment fits the next. Grading done right is invisible to the customer and decisive to the business.