A brand fits one sample size, then has to sell it in ten. Pattern grading is how the approved pattern becomes the whole size range without fitting each size from scratch. Done well it is invisible; done badly it is the reason a size 18 fits nothing like the size 8 it was scaled from.
This guide explains what pattern grading is, how grade rules work, the three grading methods, what grading cannot do, and where it sits in the tech pack and production.
What is pattern grading?
Pattern grading is the process of scaling a base, or sample, size pattern up and down to create a full range of sizes, while keeping the garment's fit, proportions and style details intact. One pattern, fitted and approved in a single size, becomes the whole size run.
It is a distinct step in production, not part of the original patternmaking. Once a sample is fitted and signed off, grading is usually the first thing that happens before the garment goes to cutting, and each size ends up with its own set of pattern pieces.
Why does grading matter?
Grading decides whether every size in a range fits as well as the one that was fitted. It is quiet, technical work, but it is where a size range succeeds or quietly falls apart.
- Consistent fit across sizes: a good grade keeps the proportions and fit intent of the sample at every size; a poor one leaves some sizes tight, boxy or off-balance.
- Size inclusivity: extending a range only works if the grade holds; a bad grade is a common reason larger sizes fit worse than the core range.
- Returns and reviews: size and fit is the single biggest reason clothing is returned, and it usually traces back to the fit block and its grade across sizes, not the sewing.
- Cost: the grade sets how much fabric each size uses, so it feeds directly into the cost of the range, size by size.
None of this is glamorous, but it is decisive. Two brands can cut the same style from the same fabric, and one will fit its whole range while the other only really fits its sample size. The difference is the grade.
How grade rules work
Grading is driven by grade rules: numbers assigned to specific points on the pattern, called grade points or cardinal points, that define how far each point moves for each size up or down. The rules are worked out from the size chart, then applied at every point.
- The grade: the total change between two adjacent sizes, for example a 5 cm (2 inch) increase at the bust, is called the grade; it is split across the pattern so each seam takes a share.
- X and Y movement: each grade point moves horizontally (X, for girth) and vertically (Y, for length) by a set increment per size; a graded spec sheet lists these increments before any cutting begins.
- It is not uniform: different points grow by different amounts, because a body's parts do not scale together; the neck grows far less than the chest between sizes, so their grade rules differ.
A simple example: if the bust grows 5 cm between two sizes, that grade is not added in one place. On a front-and-back bodice it is typically split four ways, a quarter at each side seam on the front and back, so the shape stays balanced as it scales. Every girth measurement is distributed like this.
The three grading methods
There are three ways to apply grade rules, and they all produce the same correct result; they differ in speed and tooling. Industry runs almost entirely on the third.
Whichever method is used, the choice of base size matters. Grading outward from a mid-range size, rather than from the smallest, keeps every size closer to the fitted original and limits the distortion that builds up the further a size sits from the base.
- Cut and spread: the simplest method, and the basis of the others: cut the pattern along set lines and spread the pieces apart to grade up, or overlap them to grade down. It needs only a ruler, pencil and scissors.
- Pattern shifting: move the whole pattern a fixed distance in each direction and redraw the outline, reaching the same result as cut and spread without cutting the paper.
- Computer (CAD) grading: the fastest and most precise, and the industry standard; software such as Gerber, Lectra, Optitex or Tukatech digitizes the same logic and grades the full range in seconds.
- Nested sizes: however it is done, the graded pieces are overlaid, or nested, so the grader can see the sizes step out evenly and catch a rule that has gone wrong.
What pattern grading is not
Grading is often misunderstood as a way to fix fit or design new sizes. It is neither. Grading scales an already-fitted shape; it does not improve the fit, and it does not redraw the garment.
- Not fit correction: if the sample fits badly, grading multiplies the problem across every size; fit is solved on the base pattern first, and only then is it graded.
- Not a uniform scale: a simple percentage enlargement fails, because body proportions shift with size; real grading applies different rules at different points.
- It breaks down at the extremes: a single grade run cannot stretch from a small base all the way to the largest sizes; extended and plus sizes usually need their own fitted block, not just more grading, which is a specialist skill in its own right.
Where grading fits in production
For a brand, grading is a controlled handoff between fit and manufacturing, and the size range and grade rules belong in the spec, not in a grader's head.
The sequence is fixed: the sample is fitted and approved, the pattern is graded into the full range, the sizes are nested and checked, and only then are the pieces sent to marker making and cutting. A grading error caught at the nest stage is cheap; the same error found after cutting bulk fabric is not.
- Spec the size range and grade rules: state the sizes to be produced and the grade increments in the tech pack, so the grader and factory work to the same numbers.
- It feeds marker making and cost: the graded pieces are what the marker is built from, so the grade drives fabric consumption, and therefore cost, across the size range in manufacturing.
- Base it on a real size chart: the grade rules should come from a validated body size chart and the brand's fit intent, not guesswork, since the whole range inherits whatever the base and the rules encode.
- Keep the grade with the style: the graded nest and grade rules are part of the style's record, so a re-order or a fabric change starts from the right sizes, not a fresh grade from scratch.
Grading is one link in the chain from sample to shipped range, tied to fit, size charts, marker efficiency and cost. Apshan structures that product and production knowledge, cited to source, so the decisions behind the range are informed. Request access or see the plans and pricing.