How to Build a Sewing Pattern, Step by Step

What you will learn

Understand the general method for building any clothing pattern from scratch: which measurements to take, how the base pattern is drafted and in what order to proceed, before applying it in the next two lessons to a skirt and a pair of pants.

Before you start

No previous experience needed. All you need is a tape measure, pattern paper, a square or ruler, and something to draw with; in the next two lessons you will use this same method to build the pattern for a skirt and for a pair of pants.

Concept

Building a clothing pattern from scratch means translating a body (or a garment that already fits well) into a flat pattern: first you take the measurements, then you draft a base pattern with no design, called a sloper, and only on that sloper do you build the style with its neckline, sleeves or other details specific to that garment. It is a method, not a different recipe for each garment: the same order — measure, draft the sloper, turn it into a style, test it, correct it and, if needed, grade it and digitize it — works for a skirt as well as for a pair of pants or a t-shirt. What changes in each case are the specific measurements and the drafting formula. This lesson shows the complete method once, in general terms, so that in the next two you can apply it step by step.

Lesson content

Which measurements you need before drafting anything

Before drafting any sloper you need a consistent set of measurements, always taken with the same tape and the same tension: from a person, from a reference size chart, or from a garment that already fits well, which is known as rub-off patternmaking (taking the pattern from an existing garment).

How the base pattern (sloper) is drafted

The sloper is drafted on paper with a square, a French curve and a tape measure, applying a formula that distributes those measurements among the key points of the body: bust, waist, armhole, shoulder. A minimum amount of ease is added, which varies depending on the garment and the fabric you are going to use.

The sloper has no design: it carries only the structural darts needed for the fabric to sit on the body. From a single torso sloper, for example, different styles of that same garment family are derived later.

From the sloper to the style: what gets transformed

To go from the sloper to the style, that base draft is transformed: darts are moved or distributed into a design seam, the desired neckline is drawn (round, V-neck, boat neck) and the sleeve type (set-in, raglan, batwing) is drawn onto the armhole, adding pieces such as pockets, pocket flaps or yokes.

Each transformation adds pieces or cuts the sloper into separate parts. That is where the pattern stops being generic and becomes the pattern of a specific style: the skirt and the pants in the next two lessons start from exactly this step.

What comes next: test, correct, grade and digitize

The transformed style is not considered finished: first a sample is sewn in an inexpensive, neutral fabric (muslin, percale or nonwoven fabric) and tried on a dress form in the base size or on a real person. What that fitting shows is used to correct the pattern — adjusting a dart, moving a seam, correcting a length — often in more than one round.

Only once the base size is approved is it graded across the whole size range (XS to 4XL for adults, 2 to 18 for kids, depending on who you sell to) and, if you are going to produce in volume, converted to digital format. The order matters: there is no point in grading a pattern that has not been tested yet, or digitizing one that has not been corrected.

Step by step

  1. Take the measurements of the body or of the base garment: bust or chest circumference, waist, hip, waist length and back width at a minimum, adding sleeve length and arm circumference, or rise, circumference and leg length, depending on the garment.
  2. Draft the base pattern (sloper) on paper, with a square, a French curve and a tape measure, distributing those measurements among the key points of the body: bust, waist, armhole, shoulder.
  3. Add a minimum amount of ease to the sloper, suited to the garment and the fabric, and leave it with only the structural darts needed, still with no design.
  4. Transform the sloper into the style: move the darts to a design seam, draw the neckline and draw the sleeve onto the armhole, and add the pieces that are needed (pockets, pocket flaps, yokes).
  5. Sew a sample in an inexpensive, neutral fabric (muslin, percale or nonwoven fabric) and try it on a dress form in the base size or on a real person.
  6. Correct the pattern based on what the fitting shows you: adjust darts, seams or lengths, as many times as needed.
  7. If you are going to produce in volume, grade the corrected pattern across the whole size range and convert it to digital format.

Practical example

The same torso sloper can end up as very different styles depending on how its darts, neckline and sleeve are transformed. And that same method — measure, draft the sloper, transform, test, correct and grade — is the one you will apply in the next lesson to build the pattern for a skirt, and in the one after that, for a pair of pants.

Common mistakes

Confusing the base pattern (sloper) with the finished pattern of the style.: The sloper has no defined neckline, sleeve or pockets: it is the base with no design from which all the styles of that garment family are transformed.

Grading or digitizing a pattern before having tested and corrected it.: The order is to test with a sample, correct based on that test, and only then grade across the whole size range; otherwise the fit error is repeated in every size.

Using any fabric for the sample, without thinking about how it behaves.: Use an inexpensive fabric with neutral behavior, such as muslin, percale or nonwoven fabric, so the test is not distorted by a stretch or a drape that the final fabric does not have.

Modeltex tip

Always keep the base pattern (sloper) untransformed: you will derive both the skirt and the pants of the next two lessons from it, along with any other style you want to build later. And if, besides building the technical pattern, you want to think like a designer — color, silhouettes, putting a collection together — Modeltex Lab also has the free Fashion Design course.

Exercise

Take your own torso measurements (or someone else's) as you saw them in this lesson — bust or chest, waist, hip, waist length and back width — and write them down on a measurement sheet. You will use those same measurements in the next lesson to draft the base pattern for a skirt.

Frequently asked questions

How is the base pattern (sloper) different from a finished pattern?

The sloper is the pattern with no design, drafted only with the body measurements and a minimum amount of ease, with the structural darts needed. The finished pattern has already been through the transformation: it has the neckline, the sleeve and the pieces specific to a particular style.

Can the base pattern be drafted by hand, or do I need computer software?

It is drafted by hand, on paper, with a square, a French curve and a tape measure. CAD programs (such as Optitex, Audaces, Gerber or Lectra) come in later, to grade the size range and to digitize the pattern if you are going to produce in volume.

What happens if I skip the sample and correct directly on the graded pattern?

Any fit error in the base pattern is repeated in every size of the range. That is why the order is to test with a sample in an inexpensive fabric, correct based on that test, and only then grade.

How long does it take to build a complete pattern, from measurements to production?

Usually several weeks per style, between measuring, drafting the sloper, transforming it, testing one or more samples, correcting and grading across the whole size range, especially if more than one round of fittings is needed.

Does the same method work for any garment?

Yes, the general order — measure, draft the sloper, transform, test, correct and grade — is the same for a skirt, a pair of pants or a t-shirt; what changes with each garment are the specific measurements and the drafting formula of the sloper.

Summary

Building a clothing pattern from scratch always follows the same method: take the measurements of the body or of the base garment, use them to draft the base pattern (sloper) with no design, transform it into the style, test it with a sample, correct it and, if needed, grade it across the whole size range and digitize it. With this method clear, the next two lessons will apply it step by step to a skirt and to a pair of pants.

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