Pattern grading turns a base sewing pattern into additional sizes using planned increments. It does not enlarge every outline by one percentage. Key points move by different horizontal and vertical amounts so proportions, seam lengths, and construction lines continue to work together.
Grading in pattern production
The process starts with a sample or base size. Rules define how bust, waist, hip, shoulder, neckline, armhole, and length change for each size. These rules depend on garment type, target customer, and the brand’s size chart.
After grading, seam lengths, notches, darts, and panels must be checked. A sleeve cap still needs to correspond to its armhole, and a waistband to the waist edge it joins.
Blending between supplied sizes
Home sewists often use “grading” to mean blending between sizes. A person might follow size 12 at the bust, size 14 at the waist, and size 16 at the hip, drawing a smooth transition between those lines. This is a personal fit adjustment within a nested pattern rather than the complete production process used to create a size range.
Transitions must occur at consistent body levels on all corresponding pieces. Seam lengths and matching marks are then trued. A large jump or a complex panelled design may require a more specific fit adjustment.
Why PDF scaling is not grading
Printing a PDF at 105 percent enlarges width, length, seam allowance, markings, and test square by the same ratio. Human measurements do not change proportionally in every direction, and an included seam allowance generally should not grow. Uniform scaling is therefore not a sound way to create another garment size.
Digital patterns should be printed at their specified scale. Use supplied size lines, proper grading rules, or a targeted alteration to obtain a different fit.
Practical limits
The farther a new size is from the base, the more likely simple rules are to distort proportions. Professional ranges may use separate blocks for different size groups for this reason. After substantial grading, sew a test garment before cutting valuable fabric.