Grading a pattern means creating a family of sizes from a base. The tempting shortcut — scale the base pattern proportionally — looks reasonable on paper and is almost always wrong in practice. Here is why, and what to do instead.
The problem with proportional scaling
The human body does not grow proportionally between sizes. From a size M to a size L, the chest circumference grows by roughly 4 cm. But the neck circumference grows by only about 1 cm. The shoulder width grows by about 1 cm. The sleeve length grows by about 0.5 cm. The torso length grows by about 0.5 cm. Proportional scaling would inflate all of these by the same percentage — which would make the neck opening huge, the shoulders too wide, and the sleeves too long relative to the chest growth.
Standard grade rules
Industry-standard grade rules encode these asymmetric growth patterns. For a menswear jersey garment, the typical rules per full size increment (M to L) are: Chest width +2 cm per side seam (4 cm total). Shoulder width +0.5 cm per shoulder seam. Back neck width +0.3 cm. Armhole depth +0.5 cm. Sleeve width +1 cm total. Sleeve length +0.5 cm. Body length +0.5 cm.
These numbers are starting points, not absolutes. Your brand's fit philosophy, target customer, and design language all influence where you deviate. But they are defensible starting points backed by population measurement data.
The base size question
Choose your base size before you start grading, and choose it deliberately. Most European menswear brands grade from a size M (chest 98 cm finished). Grading up from a smaller base is more common than grading down from a larger one, because fit problems tend to accumulate as you grade up — you want to fit-approve at your base before committing to the full size run.
A well-graded pattern is one where every size looks like it was drafted independently. If the S looks like a shrunken M, the grade is too proportional. The test is to put all sizes on the same form and check that proportions hold across the range.