Making Sense of Pattern Grading
Four ways to address an uneven grade
When you have an even grade, the process of grading is straightforward. Home sewers and dressmakers often, however, encounter uneven grades, when, for example, a dress needs to be graded up 2 in. at the bust, but 4 in. at the hip. If the grade is uneven, there are four ways to use grading to alter the pattern:
1. If the grade is uneven and you're sizing up, then you can use an even grade equal to the value of the largest measurement difference. If you're sizing down, then use an even grade equal to the value of the smallest difference. This will get the pattern close to the general size you need, then you can make minor adjustments as needed.
2. My favorite method allows for a more exact fit and is the best way to address fit problems for pear- or triangle-shaped women. Just separate the pattern at the waist, and grade the top and bottom individually. Then rejoin the pattern, and blend the new lines at the waistline.
3. You can address an uneven grade based solely on the difference between the bust measurement of the pattern and the body. Because the bust is the hardest part of the body to fit, many patternmakers evenly grade the pattern to fit the bust, then alter as necessary at the waist and hip.
4. This method is specific to a common grading challenge that occurs when a body has changed in width or height, but not both. With a client who's gained weight, for example, just grade for circumference and forget about grading for length. Or for a teenage daughter who's grown 6 in. taller but hasn't filled out otherwise, ignore circumference and only grade for length.
If the differences between these measurements aren't equal, then it's an uneven grade. This changes the shape of a garment, as well as its size, so strictly speaking, uneven grading isn't really grading. "Uneven grade" is synonymous with "pattern alteration." An even grade is the type of grade I will discuss because it's straightforward and easy to understand. Once you master the even grade, applying the methods to the uneven grade is the next step. See Four ways to address an uneven grade for more information.
Putting it all together
Once you've determined that you have an even grade, the actual mechanics of cut-and-spread grading are easy (see The cut-and-spread method for detailed instructions). Basically, you will use your measurements to do some easy calculations, create the cut lines on your pattern, then spread/overlap at each cut line the calculated amount. I've listed the necessary formulas in the grading chart, as well as pre-calculated values (no math needed) for three different overall grades (1 in., 1-1/2 in., and 2 in.).
The cut-and-spread method can even be used when grading large amounts up or down, for example a size 4 to a size 18. The large gaps at the cut lines do tend to be a little awkward, so I recommend grading incrementally instead (first grade the size 4 to a size 12 and then the size 12 to a size 18).
Insider tip (industry secrets and know-how)
There are no standard sizes in the garment or pattern industry. Each manufacturer sets its own base pattern measurements and grading conventions based on a specific customer base.
Size-to-size grades for patterns or garments usually differ within a company's product line. Smaller grades, 3/4 or 1 in., are associated with smaller numerical pattern or garment sizes. That is, a size 4 may only be graded down 3/4 in. to produce a size 2. Intermediate grades, 1-1/2 or 2 in., are typical of middle numerical sizes. Larger grades, 3 in. or more, separate larger sizes. This is why one company's size 8 can be different from another's (i.e., different base pattern measures) and why the difference between a size 8 and 10 vary from one company to the next (i.e., different grading rules).
Take it to the next level
When you first try grading, start with a basic bodice front and back, skirt front and back, and sleeve, then graduate to more complicated designs. Remember that any pattern, no matter how "designed," is based on one or more of the five basic pieces. Even a strapless top began life as a basic bodice, so place the strapless bodice pattern over the basic bodice pattern and transfer the cut lines. A dress is simply a bodice joined to a skirt, so the cut lines and spread/overlap amounts remain the same. Just match up the vertical lines on the bodice with those on the skirt.
Grading can be as complicated or as simple as you want it to be. So when you first approach any pattern, always start with these basics. Figure out your needs as a sewer, dressmaker, or designer; then map out your course, and grade, one step at a time.
Terry Horlamus is founding director of Seattle's New York Fashion Academy and teaches grading, pattern design, illustration, sewing, and construction.
Photos: Scott Phillips; drawings: Linda Boston