Fitting Formulas

Choosing a starting size

When I started making pants, I took the usual trial and error approach. After a few iterations, I had pants that fit. The final pattern looked quite different to the starting point. No worries, I told myself, because my body is uniquely weird so that makes total sense. But I also had to admit that this was not a satisfactory answer for a couple of reasons.

1. I can buy off-the-rack pants that fit. If my body was really so uniquely weird, there is no way that RTW would be making garments that fit my body.

2. I had zero understanding of why the changes I had made to the pattern “worked”.

There are various ideas floating around that address these concerns. One of them was that RTW pants were somehow made from different patterns that are “better” than those available to the sewing community. “Better” might mean more representative sizing or different drafting. And anyways, once you had your well-fitting pants pattern it didn’t really matter whether you “understood” it or not as you could just take the crotch curve and change the leg styling so there was no need to go through the fitting rigmarole again.

Around that time, I started to take classes and find out what sewing educators had to say on the subject of fitting. One of my favorites is Nancy Zeiman who popularized the Pivot and Slide alteration system developed by Ruth Oblander. If you are familiar with Pivot and Slide and have tried #TopDownCenterOut you can see how the pattern preparation is a lot like sliding (although no pivoting!).

The Sew/Fit approach

The Sew/Fit manual was published in 1978.

Unsurprisingly./suprisingly, few things have changed. From the introduction:

In the Sew/Fit method, “proper” fit is accomplished by:

1. Purchasing patterns to fit the front shoulder area, not according to the bustline measurement

2. Adjust the pattern prior to cutting fabric by pivoting and sliding

“By purchasing the correct pattern size and making the correct alterations as instructed in this manual, you will achieve a proper fit”

The correct pattern size

A key component of Sew/Fit is starting with the correct pattern size.

In fact, selecting an appropriate starting size is the basis for all fitting approaches whose departure point is a commercial pattern. In the 1970s there was more stress associated with this decision than today because patterns were sold with only a single size in the envelope.

The Sew/Fit book emphasizes choosing the “correct” pattern size.

Instead of using bust/chest measurement to select the pattern, the Sew/Fit method uses a front armhole measurement, this approach developed empirically from the experience of measuring 1000s of bodies and studying commercial patterns.

The front armhole measurement is then used to select the “correct” pattern size from a chart and frequently it winds up being a smaller size than suggested by bust circumference:

After determining the starting size, the process becomes one of measuring the figure and flat pattern, then and using this information to adjust the pattern, essentially a process of custom grading.

The availability of multi-sized patterns has made custom grading easier. If the multi-sized pattern is nested appropriately, it is straightforward to blend between different sizes at different locations¹.

Lots of people use this approach for fitting. This is the rationale behind the commonly advice to “start with a smaller size to fit neck and shoulders, then adjust for the bust/ do an FBA as needed”. It is straightforward to understand and execute. It avoids the complications of other types of adjustments that require you to slash the pattern. Overall it is terrific and works really well, and especially for tops and dresses.

One reason why the Sew/Fit method worked especially well is because it was developed at a time when everyone used patterns from the same companies and mostly wore skirts and dresses (i.e. not pants). The sizing was well-understood and consistent between companies. Not only was the sizing consistent but as can be observed in the table above, patterns were available in different categories catering to different body types that vary in their proportions.

The Sew/Fit customer may have a certain front armhole measurement but then would be able to select a size from the category that most corresponded to their figure type. Choosing the size to fits neck and shoulders PLUS the suitable body type would provide another level of custom adaptation not available to us today where patterns are only available in the “Misses” range. This is a nice illustration of how fitting approaches can be rooted in historical assumptions that may not necessarily be relevant when circumstances change. The equivalent of this in the contemporary world would be using a pattern company that caters to a specific body type.

The authors of the Sew/Fit method were aware that the fit may still need improvement after the custom grading process so the book has a section on wrinkles:

Here we get into the familiar territory of “reading the wrinkles—”A crosswise stress wrinkle just below the waistline means that the garment is too tight around the high hipline” etc. The wrinkles are always attributed to one of three categories; “incorrect measuring”, a “body part issue”, or, (of course) “choosing the wrong pattern size”.²

So, at the end of all this (which is quite a journey), the Sew/Fit approach has applied a formula that was developed empirically, i.e. constrained to the population and pattern style used to develop the formula. It is a terrific formula and many use it with great success.

TopDownCenterOut is not a formula

Given the variation in clothing design and body shapes, the number of variables is basically infinite. This leads to fitting conundrums where one person can have a wrinkle that is solved with one body part adjustment and a different person can have a similar wrinkle and do the same adjustment with a different outcome. Sewists call this the “fitting puzzle”.

This is why TopDownCenterOut does not offer any formulas. This aspect of TopDownCenterOut definitely makes it frustrating because we all want to hear “just make this magic body part adjustment for the perfect fit”. I wish it were possible.

If we constrain ourselves to a single style or block³ it certainly is possible to take shortcuts and make fitting adjustments more formulaic. This is one reason why sewing teachers will focus on fitting a single pattern or style.

But, if we want an approach that delivers more generally for all bodies and styles, we have to develop understanding. TopDownCenterOut does not provide a straightforward answer such as “slash and move the pattern pieces apart by half the measurement of the material pinched out” or “measure the body and compare to the pattern, then adjust the difference”. In essence it is a tool that illuminates the various factors influencing the fit so the maker can decide how the design, body and fabric collaborate to create the optimum fit. Not only is the maker empowered to be in control but this understanding provides insight into the decision. If the final fit is not what was anticipated, the maker can modify as appropriate. A nice example of this is MarieMadeThis who made a first pair of trousers with TopDownCenterOut. Were they a “perfect” fit? No, but they were wearable and importantly, she was empowered to understood and analyze what to do differently for the next pair. Plus the process was not discouragingly arduous—“it has taken away a little bit of the scary factor about making trousers…”.

1. Look for my article on blending between sizes in the upcoming issue of The Pattern Pages

2. The usefulness of wrinkle charts is very limited: two individuals may be making the same pattern and have the same wrinkle but the optimum solution for each may be different. And similar winkles in different designs may need very different adjustments.

3. And vice versa, if we only focus on a single body type, hence the sewists who announce “I made all my usual adjustments”.