How to Grade Sewing Patterns

What you will learn

Understand what grading (or scaling) a pattern means, how to build and apply a grading table of increments, and the two ways to grade — by hand and in CAD software — so you can generate a complete size range without losing the balance of the garment.

Before you start

Have the base pattern for a middle size already built (for example size M in women's or size 40 in men's). You don't need CAD software for this lesson: basic patternmaking knowledge is enough.

Concept

Grading (also called scaling) a pattern means generating the rest of the sizes in a size range from a base pattern by moving each point of the piece the distance set by a grading table of increments. It is not the same as enlarging the whole drawing by the same proportion: the body does not grow equally in every direction, and each point — armhole, neckline, side seam — has its own displacement. The base pattern is usually a middle size, such as M in women's or 40 in men's. The goal is not only that the garment fits another body: you also have to keep the same balance and the same proportion between pieces in every size, and the pieces that are sewn together must still match up.

Lesson content

The grading table: how much each measurement grows

The grading table states, for each key measurement of the garment, how many centimeters it grows or shrinks from one size to the next. It comes from the size chart of the brand or of the market the style targets, and it changes depending on whether the garment is women's, men's or kids', and on the type of garment.

As an approximate reference (every table is different), at the extremes of the size range — 3XL, 4XL — the circumference usually grows faster than in the middle sizes, because the body increases more in circumference than in height.

Grading by hand: guidelines and ruler

You work on the paper base pattern. First you draw horizontal and vertical guidelines — the bust or hip line, the center front — that serve as a fixed reference for moving each point of the outline.

From those lines, each point is moved the distance given by the grading table, using a ruler and a square to keep the right angle, and the new points are joined with a French curve or hip curve. It is accurate if done carefully, but repeating it across eight or nine sizes per piece multiplies the work and the risk of error.

Grading in CAD: Optitex, Audaces, Gerber

In pattern design software, grading is loaded once per piece: you assign horizontal and vertical growth rules to each point of the outline, and the system automatically generates the rest of the sizes in the range.

The advantage is that it applies the same criterion to all the pieces of the style at once, lets you review the overlaid sizes on screen, and exports directly to DXF/AAMA, PDS or ADS — the format later used by a computerized marker. But if the grading table you load is poorly thought out, the error is repeated just as fast across all eight sizes.

Common mistakes and how to check the result

The most frequent mistake is losing balance: if the guidelines are not firmly fixed before the points are moved, each new size drifts a little from the previous one and the piece loses its proportion. It shows most in darts, openings or pockets that are placed with precision.

The second is not keeping the notch aligned between sizes — the mark that shows where a sleeve goes into the armhole, or where a collar meets the neckline. It has to move with the same rule as the rest of the outline; if it is marked by eye, the mismatch is only discovered when sewing.

Step by step

  1. Draw the horizontal and vertical guidelines on the base pattern (bust or hip line, center front).
  2. Move each point of the outline the distance given by the grading table, using a ruler and a square to keep the right angle.
  3. Join the new points with a French curve or hip curve to draw the outline of the new size.
  4. Repeat the process size by size, up and down the size range.
  5. Compare the growth between consecutive sizes: measure the same line (bust, waist, length) and check that the difference matches the grading table.
  6. Check that the pieces sewn together still match up in every size (armhole with sleeve, collar with neckline, side seam of the front with the back).
  7. Sew a sample of the base size and one of the extreme sizes, try them on, and correct the table if the fit changed.

Practical example

In a typical grading table, the bust circumference may grow between 4 and 6 cm from one size to the next, while the total length only goes up 1 to 2 cm. That is why an L is not an M enlarged by the same proportion: each measurement grows according to its own value in the table.

Common mistakes

Grading by enlarging the whole drawing by the same proportion with a photocopier or an image: Apply the grading table point by point: the circumference grows quite a bit more than the length, so enlarging everything equally leaves the garment too long and distorts the armhole or neckline.

Moving the outline points without fixing the guidelines first: Draw the horizontal and vertical guidelines on the base pattern first, and only then move each point according to the table, so you don't lose balance between sizes.

Placing the notch by eye in each size: Move the notch with the same displacement rule as the rest of the outline, so the sleeve and armhole (or collar and neckline) keep matching in every size.

Modeltex tip

If you need to launch a style with the size range already solved, without developing the grading from scratch, Modeltex digital patterns come with the complete size range graded and approved with a sewn sample (eight sizes for adults, from XS to 4XL, and nine for kids, from 2 to 18), in PDF or in DXF/AAMA, PDS and ADS to load straight into Optitex, Audaces or Gerber.

Exercise

Take the base pattern of a simple piece — for example a t-shirt sleeve — and a reference grading table. Draw the guidelines, move the outline points to generate one larger and one smaller size, and check that the armhole notch stays aligned across the three sizes.

Frequently asked questions

In a nutshell, what does grading a pattern involve?

Moving each point of the base pattern the distance set by a grading table, following horizontal and vertical guidelines, to generate the rest of the sizes without losing the shape of the piece. It can be done by hand, with a ruler and square, or in CAD software that loads the table once and generates the whole size range.

What exactly is the grading table?

It is the table that says how many centimeters each key measurement of the garment — bust or chest, waist, hip, length — grows or shrinks from one size to the next. It comes from the size chart of the brand or of the market the style targets, and it is the basis of all grading.

Do all sizes grow by the same amount?

Not necessarily. As an approximate reference, the circumference grows 4 to 6 cm per size and the length only 1 to 2 cm, but at the extremes of the size range (3XL, 4XL) the circumference tends to speed up, because the body increases more in circumference than in height.

Can I grade by enlarging a photocopy or an image of the pattern?

Not reliably. That method enlarges the whole drawing by the same proportion, and the body doesn't grow that way: the circumference grows quite a bit more than the length. The result usually comes out too long, with a distorted armhole or neckline.

Is it worth learning to grade by hand if I'm going to use CAD later?

Yes: understanding the logic — guidelines, point-by-point displacement, notches — is what lets you check whether a table loaded into the CAD software makes sense. The program executes faster, but it doesn't correct a wrong grading criterion.

Why do I have to be careful with the notch when grading?

Because it is the mark that shows where two pieces must match when sewing — for example, where the sleeve goes into the armhole. If it is placed by eye in each size instead of being moved with the same rule as the rest of the outline, the mismatch is only noticed on the sewing line.

Summary

Grading a pattern means applying a grading table point by point to the base pattern, by hand with guidelines and a ruler or all at once in CAD, and then checking that the growth between sizes and the fit of the pieces are right across the whole size range.

Go back to the full course or ask the Modeltex Lab AI.