What are grade specs, grade rules and grade rule libraries?

Posted by Kathleen Fasanella on Feb 10, 2011 at 4:56 pm / Glossary, Grading / Trackback

In the process of writing a post, I find I need this post in order to be able to refer to it.

There are three levels or layers of size specification:

  1. Grade specifications (varies from general to specific)
  2. Grade rules
  3. Grade rule libraries

I will do grade specifications last.

girth_rules_mapped2A grade rule is a designated amount a pattern is made larger or smaller at one given point in order to make it fit a range of sizes.

[The "one given point" at which a grade rule is placed is called a cardinal point. The grading police will not come and get you if you don't know this.]

In the illustration at right, there are grade rules placed at the (cardinal points) neck and shoulder juncture, the outside shoulder tip and midway down through the armhole. The illustration is only a visual example that shows how a manual pattern is mapped. A CAD pattern is graded at the same cardinal points of course but it doesn’t look like this on screen. A discussion of grade mapping is in my book in the section titled A practical guide to grading starting on pages 170-175. Because designers are not expected to specify grade rules, there will not be a test on this later.

A grade rule library is a collection of grade rules that will be used to grade a pattern according to the desired size specifications. I realize that the word “Library” conjures up the idea of a large collection but a library amounts to a chart of data. It’s a library in that it is a “collection” but not in that it is large.

Each library will vary according to the type of grade, features and fabric properties of a design. For example, you will need two different libraries for two identical tops if one is knit and the other is a woven. Or, you will need two different libraries if one of the tops is graded SML and the other in numbered sizes. Grade rule libraries are usually made by copying and pasting data from one or more rule libraries to create new ones. Again you don’t have to worry about this. I cannot think of an instance in which a designer would be responsible for creating grade rule libraries unless they wanted to.

Grade specifications are relatively general but can be more complex depending. A grade spec is a measure you specify to indicate how much you want each size to grow or shrink (this is also in my book in the grading section I mentioned). You should know something about sizing to know whether you want each size to increase an inch or two and also for height. There are several earlier entries about this on this site that I will link to at close.

More complex grade specs are appropriate if you are targeting a specific niche but again, you need to know something about grading and in that case, probably won’t be reading this except to double check yourself because it seems like half the time that the rest of the world has gone crazy so you begin to wonder if it’s you or everyone else.

The bad news is that designers are expected to provide basic (simple) grade specifications. This is your job. If you don’t know or have them, you can usually hire a pattern maker or grader to help you develop them. However, it is very important that you know this is not our job. Many designers are annoyed if service providers can’t guess what one’s grade specs should be or angry that we don’t provide this service for free. Collecting information like this can be expensive but you can do it yourself for a relatively low cost. Worst case, you can buy a range of sizes of an existing product line of which you like the grade, take these to a pattern grader who can then measure each garment to reverse engineer the grade.

Related:
How to create grade rules pt.1
How to create grade rules pt.2
How to create grade rules pt.3
Things you must know if you have a clothing line: garment measuring
Espionage for better sizing
Espionage for better sizing pt.2

11 Responses to “What are grade specs, grade rules and grade rule libraries?”

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Sabine
February 10th, 2011
7:48 PM

I love you for generally always posting just what I will need to know next…just wanted to throw that out there

Timo Rissanen
February 10th, 2011
8:31 PM

Hello Kathleen,
Responding here since you might not see a response on my cobwebby blog – yes, in NYC to stay (for a few years at the very least) and NM is definitely on the wishlist – to see you! I’ve also just realised why my last post might have suggested I was going back home. Traveling west a few times this year; will keep you posted. Please do let me know if you venture this way, too. In the meanwhile, would love a phone conversation soon.
t

Penny
February 11th, 2011
3:55 PM

I’ve never know a designer to supply a grade. It’s always been either the technical designer, patternmaker or someone in production.

[...] Member Forum « What are grade specs, grade rules and grade rule libraries? [...]

Sandy
May 23rd, 2011
9:14 AM

hi Kathleen,
What is the grade rule for Chest and Across Shoulder of Men’s wear, size S-XL. I always get different comments from China factory. Some says s/b 1″ grade for both chest and across shoulder, but some factory recommends 1″ grade for Chest, but 1/2″ grade for Across shoulder. Should that be different grade rules for woven and knit as well? Please advice me.

Kathleen
May 23rd, 2011
1:02 PM

I think you mean the total grade. A grade rule applies to a given cardinal point (as explained in this entry).

There are too many points I’m not clear on. Ex: “Some says s/b 1″ grade for both chest and across shoulder,” does this refer to front and back respectively or jointly? In any event, 1″ (or even 1/2″ imo) is crazy for the shoulder. Generally, men’s sizes are two inch jumps (40-42-44 etc) so minimally 2″ req’d. More for SML since those include one and half to two sizes. I think a grading book would be helpful, not sure we can figure it out here but maybe in the forum.

[...] Grading children’s clothes pt.1 What are grade specs, grade rules and grade rule libraries? How to create grade rules 1 How to create grade rules 2 How to create grade rules 3 addthis_pub = [...]

Denise
October 29th, 2011
10:39 AM

I have a question about how grading works. A paper pattern of mine was scanned in as a size medium. So when it gets graded, does the pattern need to be measured for some sort of starting point for the grading rules? If a generic grading rule is applied to the pattern, would my original size medium change to match the generic grading rule?

Kathleen
October 31st, 2011
4:30 PM

Hopefully I won’t muck this up with over complication.

If your medium is ready to go and doesn’t need corrections, it should not change at all -mostly because it is not graded. It is the basis -the ruler- for the other sizes.

Now, your medium pattern may be measured but for other reasons. One, it is measured to establish the baseline for tolerances. Ex, your medium side seam is 10″. If it grows .375 per size, it is easier to put all those measures and tolerances for meeting the specification into charts for quality control.

ashok sehgal
January 2nd, 2012
6:26 AM

grading technique for waist, chest, hip measurements
I have studied human figures minutely and came to this conclusion that while grading for the above mentioned specs one should study their cross sectional diagram carefully because elliptical figures expansion /reduction behave in different manner altogether with respect to plain flat two dimensional grading.

keletso glen
March 2nd, 2012
2:22 AM

hi there i will love to hear much about grading rule

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