Size grading

Size grading is how one sample becomes a size range. A brand fits a sample size, then adds or takes away a set amount at each measurement for every size up or down: so much at the chest, so much at the waist, so much in length. The amount per size is the grade.

How big the grade is, and whether it changes along the range, is the brand's choice. That is one reason a medium isn't the same size at every brand: two ranges that start close can be a size apart by XL.

On a size chart

Grading shows as the step from one size to the next. Ruban Size's men's T-shirts template grades its garment evenly:

That is 3 cm across (6 cm around) and 2 cm of length per size. Body ranges can grade unevenly: in the women's tops template, the chest grows 5 cm from XS to S and 7.5 cm from L to XL, center to center.

When you measure your own samples, measure the same points on every size. The steps should go up steadily; a jump or a dip is worth measuring again. How to measure a garment flat shows the points.

In Ruban Size

Find my size reads the grade from the chart itself: the size step is the usual gap between two sizes on that measurement. It uses the step to judge how far a measurement falls outside a size, and to move the answer when the fit scale says runs small or runs large. A row whose values don't grow with the size is left out; if no row is left, the chart's Fit and Find my size tab says "Find my size cannot read this table". Why a medium isn't the same size at every brand has more on grading.