How To Get Base Size Measurements For An Apparel Tech Pack Spec Sheet

Of all the detailed sections in a tech pack, it is the spec sheet that stumps the most people. A spec sheet is a crucial part of your tech pack that defines the fit and sizing of your garment. This fit and sizing all stems from the specs of your base size. So, how do you know what measurements to fill in for your base size? There are several ways you can get these measurements and we’ll go through each below.

What is included on a spec sheet

The spec sheet – also known as a spec chart – is a table of measurements that lists what each size should be at each point of measure (POM) for your garment. Usually the points of measure make up the rows and each size has a column. There is also a column for tolerances. The tolerances define what deviation is acceptable for each point of measure.

To accompany the written POM descriptions, the spec sheet also includes POM illustrations that show where each measurement is taken on the garment. This ensures that every person who uses the spec sheet to QC and measure a garment does so in the same way.

When to fill in your spec sheet

A common question I get asked about tech packs in general is “at what point during the development process does the tech pack need to be completed?” The short answer is the tech pack needs to be done before the style is sent to your factory. Depending on what your development process looks like, this could be at the beginning of development or at the end.

If your factory is making your pattern and samples, the tech pack – including the spec sheet – needs to be done as soon as the design is ready. If you are working with a patternmaker (like myself) to create your pattern and make the fit samples, then the tech pack doesn’t need to be fully complete until the pattern is ready to send to the factory.

Some of the methods to find your base size measurements below will make more sense when working with your factory on development and some make more sense when working with an independent patternmaker. In either case, the base size (or sample size) specs are often filled in before the graded specs. Once the sample and pattern are approved in the base size, the other size specs can be added.

Base size specs from the pattern

The most accurate way to find the base size measurements is to take them from the pattern itself. This method is only possible if you are working with a patternmaker who is also making your fit samples (meaning the tech pack doesn’t need to be completed and sent to your factory until after the pattern is available).

Most pattern measurements will work for garment measurements on your spec sheet, though some will need some adjusting. For example, the spec for a curved, full sweep might be slightly bigger than the pattern measurement to account for the curve stretching a bit in sewing. Or, a thick coat pattern might have turn-of-the-cloth allowance in it that won’t reflect in the final garment measurement.

Base size specs from a reference garment

If you are working with a factory on development and need to send the tech pack before a pattern is made, the most common way to create the base size specs is by measuring reference samples. When selecting reference samples to use for your spec sheet, pick one or more samples that:

  • Are the same type of product (i.e. choose a legging reference sample if you are designing a legging)
  • Fit how you want your design to fit
  • Are made in a very similar type of fabric (amount of stretch is critical here)

It doesn’t matter if the labeled size on these reference samples is different from your base size as long they reflect the fit and size you want for your base size. It is helpful, but not required, if these reference samples have similar design details to your design.

Once you’ve selected your reference samples, you can measure each POM and use those measurements as your base size specs. You can pull measurements from multiple garments, but be aware of how one POM might affect others. The more reference garments’ measurements you are combining and the more you tweak those measurements for your spec, the more likely you’ll need additional updates and fit samples during development.

Base size specs from a previous style or block

Writing spec sheets gets easier the more styles your brand has in its pattern and tech library. If your brand has produced a similar garment in the past, you can pull the base size specs from that style. Again, you only want to do this if the fabric and fit of the other style is very similar to the one you are working on. If it is, you can copy and paste specs from that other style’s tech pack.

This method works great for styles that are variations of best-sellers. For example, if you are designing a v-neck version of your brand’s crew-neck tee, you can copy and paste the crew-neck’s specs and then adjust the neck measurements for the new design. Using a best-selling block style not only makes spec-writing easy, but also creates fit consistency within your brand. There is no need to reinvent the wheel if you already have specs for a similar style.

Base size specs from body measurements + ease

One other way you can find your base size measurements – though in most cases I don’t recommend it – is by using body measurements and adding ease. If you have no reference sample, no pattern, no style history, but do have an accurate size chart of body measurements, this method can be a good starting point. This method is better used in combination with other methods mentioned above as a way to double check the measurements.

Using this method to create base size specs relies on accurate body measurements of your target customer. It also requires a skilled understanding of ease and fit. It can be done, but takes years of experience to do well. Wearing ease, beyond simple body circumference ease, is nuanced and depends on the garment style, functional intent, and fabric. It is far easier to start with a sample, block style, or pattern.

Do your best and consult your patternmaker for the rest

Unless you are filling in your spec sheet measurements based on the finished, approved pattern or prototype, there will likely be some back and forth and adjustments made during the development process. This is perfectly normal as the design and fit get dialed in. It is okay to leave some measurements on your spec sheet blank for now and fill them in later.

Fill in the POMs that you do know and are most critical to the fit of your design and ask your patternmaker or factory for their recommendations on the finer details. Communicate your design and fit intent to your whole team so that they will be able to make the most appropriate recommendations for these spec measurements. If you don’t know what a spec should be or don’t care, don’t just guess. Leave that measurement blank or write “as pattern” so your patternmaker knows to fill that in later. Creating fashion that fits is a collaborative process so don’t feel bad if you don’t know all the answers at the start.

The spec sheet in your tech pack is an important set of measurements that defines your design’s fit, sizing, and quality control standards. Depending on your brand’s product development process, there are several methods you can use to decide on base size measurements. You can measure the pattern, reference samples, use a block style, or calculate body measurements + ease plus get advice from your patternmaker and factory. All these methods will help you create base size measurements that result in a well-fitting design.

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