This page explains how to build a size set's own measurements from a base size and a stated grade rule, for anyone who checks a size set before a bulk approval: a buyer, a merchandiser, a pattern maker, or a new entrant. This lesson teaches a decision: whether a submitted size set's values actually match what the base size and grade rule say they should be, point by point.
A buyer reviewing a size set ahead of a bulk approval can assume the numbers on the page were calculated correctly, since they look like a normal table of measurements. Order A's own size set is instead built the same way every time: one base size's own fixed values, moved up or down by a stated grade rule, at every point of measure.
Without checking each point's own arithmetic, a buyer can approve a size set with one size calculated at the wrong grade amount, a problem that repeats at every garment cut to that size, discovered only once returns reach the buyer, far later than the size-set stage where it is cheapest to catch.
You need: T05-C03-L02 (grading a pattern), where this lesson's grade rule was first established. This page assumes that grade rule as its starting point.
By the end of this lesson you can:
Not covered here: what grading a pattern is and why a grade rule varies by construction point (T05-C03-L02); reading a full measurement spec with its tolerances (T05-C04-L03); common fit problems that follow a grading error (T05-C04-L04); building a full size-set worksheet for an order (T05-C04-L05).
| Term | Meaning |
|---|---|
| Size set | The complete set of measurements for every size in a size range, calculated from one base size and a grade rule. |
| Base size | The size a grade rule is applied to as the starting point for producing every other size in the range. |
| Grade rule | The set amount added or removed at each specific point on a pattern, for each size step away from the base size. |
| Point of measure | A specific place on a garment, such as half chest or sleeve length, where a size set states a value for each size. |
| Size range | The full set of sizes an order offers, for example S M L XL. |
| Size ratio | The split of an order's total quantity across the sizes offered, for example 1:2:2:1 for S:M:L:XL. |
Building a size set means applying a grade rule, established once for an order, to a base size's own measurements, point by point, to calculate every other size's value. Order A's own fixed base is size M (body length 72 cm, half chest 53 cm, sleeve length 22 cm, sleeve width 44 cm). A stated grade rule, such as the one established in T05-C03-L02 (chest +4 cm per size step, sleeve length +1 cm per size step), produces size L's values by adding one grade step to M's own values, and size S's values by subtracting one grade step. Each point of measure keeps its own grade amount; a size set is not one number scaled uniformly across every point.
A person building or checking a size set meets the same few variants across knit and woven garments, and across export and domestic orders alike, because building a size set from a base and a grade rule is a general method, not a fact tied to one specific order.
| What can differ | The shapes you meet | Why it matters |
|---|---|---|
| Base size values (given) | Order A's own fixed size-M measurements, the starting point for every calculation | Every other size's value is built from this one set of numbers, not looked up separately for each size |
| Graded-up size (L from base M) | Each point of measure increased by its own grade-per-step amount, once for a size one step above the base | A size two steps above the base, such as XL, should differ from M by twice the grade amount at each point |
| Graded-down size (S from base M) | Each point of measure decreased by its own grade-per-step amount, the same rule applied in reverse | A size below the base is not built by a separate method; the same per-point amount is simply subtracted |
| Uneven grading across points | Different points, such as chest versus sleeve length, commonly grade by different amounts, as established in T05-C03-L02 | A size set built by applying the same grade amount to every point would not match a real grade rule |
| Whether the size set is documented | An export tech pack states the base size and grade rule in writing, for a Make to Order buyer such as Northline Apparel; some factories carry the calculation in a spreadsheet formula instead | Either way, one specific value per point is expected at each size; a size set that departs from it is still a calculation error |
Northline Apparel's buyer, reviewing Order A's size set ahead of a bulk approval, checks size L's half-chest value against the base-M value and the stated grade rule, to confirm the arithmetic was applied correctly. Order A is a Make to Order export batch: Delta Garments cuts and sews the batch only once Northline Apparel's buyer has approved the size set the tech pack describes.
Order A's own fixed size-M measurements are the base this worked example starts from: half chest 53 cm, sleeve length 22 cm. The grade rule established in T05-C03-L02 adds 4 cm at the chest and 1 cm at the sleeve length for each size step. One step up from the base M produces size L.
The same grade rule, applied in reverse, produces size S: a half chest of 49 cm (53 − 4) and a sleeve length of 21 cm (22 − 1).
The methodA common mistake is applying the chest's grade-per-step amount to every point of measure, since it is the most-quoted figure in casual conversation about a grade rule. Order A's own chest grades by +4 cm per size step, but sleeve length grades by only +1 cm per size step; using the chest's larger amount everywhere overstates every other point's size progression. A size set built this way looks complete and consistent, but every point except the chest carries an error that repeats at every size step away from the base.
Building a size set means starting from one size's own measurements, called the base size, and calculating every other size's value by adding or subtracting a fixed, documented amount at each point on the garment. That amount is not the same at every point. A T-shirt's chest measurement might move by 4 cm between sizes, while its sleeve length moves by only 1 cm, because the grade rule for each point was set separately. A buyer checking a size set takes the base size's value at one point, applies the grade rule's own amount for that point the right number of times in the right direction, and compares the result to what the size set actually states. A value that does not match is a calculation error, even if the size set as a whole looks correctly built.
Northline Apparel's buyer is reviewing a submitted size set for Order A before approving it for bulk production. The facts in front of the buyer:
The document the buyer reads, the base value, the grade rule and the submitted value, exactly as quoted:
Is the submitted size L sleeve length correct? Decide before you open the answer.
No. Per the stated grade rule, size L sleeve length should be 22 + 1 = 23 cm, not 26 cm.
Two facts, together, decide this. First, the grade rule states sleeve length grades by +1 cm per size step, and L is one step above the base M. Second, the base-M sleeve length of 22 cm plus that one step gives 23 cm, but the submitted value is 26 cm, 4 cm higher than the correct figure and 3 cm higher than the correct answer would be if only the grade step were miscounted.
The 4 cm gap matches Order A's own chest grade amount exactly, suggesting the chest's +4 cm grade was mistakenly applied to sleeve length instead of the correct +1 cm. The buyer should flag the submitted size set and ask Delta Garments to correct size L's sleeve length to 23 cm before approving it for bulk.
This lesson's cost is framed qualitatively, since no fixed price is attached to a size-set calculation error in this academy's own facts. The concrete anchor is the 3 cm overstatement of size L's sleeve length in this lesson's own scenario (26 cm submitted against a correct 23 cm), a difference large enough to change how a sleeve sits on the arm.
Approving a size set with a grading error at one point produces garments that fit progressively worse at the affected point across the size range, since the same wrong grade amount compounds at every size step away from the base. That problem is usually discovered only through returns or complaints once garments have already reached the customer, far later and far more expensive to fix than catching it at the size-set stage, which is exactly what this lesson's per-point arithmetic check is designed to prevent.
Copy this row into the size-set and measurement-spec worksheet. Fill it from the size set actually submitted, not from what the grade rule is assumed to produce.
| Point of measure | Base size M (cm) | Grade per size step (cm) | Size L value (base + one grade step) | Result |
|---|---|---|---|---|
| Sleeve length | 22 | 1 | 23 |
Download the full working sheet, with rows for every point of measure this course covers, from the link on this course's page.
Download the Size-set and measurement-spec worksheet (Excel)
1. Using the grade rule chest +4 cm per size step, and a base-M half chest of 53 cm, what is size L's half chest?
2. Why can't the same grade amount be applied to every point of measure when building a size set?
3. A submitted size L sleeve length is 4 cm more than the grade rule specifies for one size step. What does this suggest?
| EN | AR | FR | TR | Meaning |
|---|---|---|---|---|
| Size set | مجموعة المقاسات | Gamme de mesures | Beden ölçü seti | The complete set of measurements for every size in a size range, calculated from one base size and a grade rule. |
| Base size | المقاس الأساسي | Taille de base | Temel beden | The size a grade rule is applied to as the starting point for producing every other size in the range. |
| Grade rule | قاعدة التدريج | Règle de gradation | Gradasyon kuralı | The set amount added or removed at each specific point on a pattern, for each size step away from the base size. |
| Point of measure | نقطة القياس | Point de mesure | Ölçü noktası | A specific place on a garment, such as half chest or sleeve length, where a size set states a value for each size. |
| Size range | نطاق المقاسات | Gamme de tailles | Beden aralığı | The full set of sizes an order offers, for example S M L XL. |
| Size ratio | نسبة المقاسات | Ratio des tailles | Beden oranı | The split of an order's total quantity across the sizes offered, for example 1:2:2:1 for S:M:L:XL. |
You now know how to build every size in a size set from a base size and a grade rule. The next lesson moves from calculating those values to reading the full document that records them alongside their tolerances: the measurement spec. Back to the course map