Garment size grading: how to grade a size chart from your base size

Size grading explained for new clothing brands: choose a base size, set grade increments per measurement, apply tolerances and avoid the usual spec sheet errors.

Updated 1 October 2026 · By Hem Apparel

Grading means creating every other size from one base size by adding or subtracting a fixed amount at each point of measure. You make and approve one size, grade the rest by rule, and the factory produces a consistent range.

Step 1: pick a base size

Use the size you will sample, usually a middle size such as M. Fit this size on a person or a form first. Everything else follows from it, so any error in the base size is repeated across the range.

Step 2: set the grade for each point of measure

A grade is the difference between neighbouring sizes at one measurement. Common starting points for a regular-fit knit top, measured flat, are shown below. They vary by fit, fabric and target market, so treat them as a starting point and adjust to your own pattern.

Step 3: calculate the table

If chest width is 52 cm in M and the grade is 2 cm, then S is 50 cm, L is 54 cm and XL is 56 cm. Repeat for every point of measure. Do this in both directions from the base size, so the spec reads correctly for the full range.

Step 4: add tolerances

A tolerance is how far a finished garment may differ from the number. ±1 cm is common for body measurements and ±0.5 cm for small details such as neck width or pocket size. Without tolerances nobody can say whether a measurement passes inspection.

When grades differ between sizes

Many brands use bigger grades at the large end of the range, or different increments for children's sizes. If the step from S to M is not the same as from L to XL, record each step instead of applying one flat increment.

Common grading mistakes

• Grading from a base size that was never fitted or approved.
• Mixing full circumference and flat measurements in the same table.
• Using one grade for every point of measure.
• Rounding differently from row to row, so the sizes look inconsistent.
• Forgetting that rib and stretch fabrics are measured relaxed.