Hey y’all – today we’re going to talk about how to make a sewing pattern bigger or smaller, otherwise known as pattern grading.
The number one question I get on my free patterns has to do with sizing. When I release a free pattern, it is always either something I drafted for myself or for whoever I made it for, like one of my kids. The patterns that I grade and test in multiple sizes take a lot more time, and that’s why those are in the shop. But regardless of what size I release for a free pattern, someone always wants a different size, so today I’m going to teach you how to do that for yourself.
The simplest explanation of pattern grading is that if you cut a pattern apart and then move all the pieces slightly away from each other, you get a bigger pattern. This is known as slash and spread grading, and it looks like the diagram below.
Similarly, if you overlap all those pieces slightly, you get a smaller pattern. Simple enough, right?
*Note: if you’re making a pattern smaller, when you read the examples below change the word “increase” to “decrease” and “spread” to “overlap”. The process is the same to make a pattern bigger or smaller otherwise.
Well, as you know, humans don’t increase in size at the same rates all across their torsos. Or hips or legs for that matter. For example, adults grow wider from size to size and not really taller. Whereas healthy kids grow taller faster than they grow wider.
So how much do you add?
Start with your measurements, then compare that to the measurement that the pattern size chart or information says it will accommodate. So for example, most of my women’s patterns are for a 34″ bust. Let’s say your bust is 38″ – that means you’re going to have to increase 4″.
But wait! Don’t spread your bodice out 4″. Most bodice pieces only cover 1/4 of the body. So you’d only need to spread this bodice piece 1″ (4″ increase/4).
But wait! You still don’t want to spread that much. If you look at a size chart (like these, for example), you’ll notice that most sizes differ by about 1-2″ per size. Two inches is about the max you want to increase a pattern before redrawing, re-slashing, and spreading again. Otherwise the pattern starts to get really distorted.
So you’ll spread your bodice 1/2″ to go up one size (1/2″ x 4 = 2″) and then increase again 2″ total from the new pattern to get to your size. And that 1/2″ you’re spreading? You divide it between all three vertical cuts you made on the pattern. You might notice that 1/2 doesn’t divide neatly into three. It’s actually preferable to divide it by 4 (so you’d get 1/8) and then use that measurement as spacing for the two vertical slashes closest to the center front/center back, (so 1/8″ each) then take the remaining amount (1/8+1/8= 2/8 = 1/4) and put that increase into the last vertical slash, the one closest to the side seam.
It gives you a new respect for cutting your fabric exactly to the pattern and being precise with your seam allowances when you realize 1/8″ here and 1/8″ and 1/4″ there ends up being a whole new size pattern. This also shows why you can’t just put a pattern in the copier and increase 110% – because the pattern shouldn’t increase at the same rate for each part.
And how much to increase in length? For children, this is going to be based on their measurements – like how much longer is your child’s torso than the pattern size?
But for adults, there’s a simpler answer since we don’t get a lot taller as we get wider. The rule of thumb is 3/8″ per size. That’s usually enough for the extra distance “out and over” that the larger sizes need to go to get to the same landmark, like the waist.
When you’ve graded a set of patterns, one way to check your work is to look at the corners. You should be able to draw a straight line on your bodices through the corners as shown below.
Note – checking the corners only works within a set of patterns – for example, toddler sizes 18m-3 or misses sizes 6-14. It won’t work when you go from toddler to children, for example. In fact, you really shouldn’t grade from toddler to children or vice versa. The reason is that grading is increasing or decreasing a pattern but keeping the same shape. If you need to go to another size group, that’s not the same shape, it’s a different shape altogether. This is more clearly illustrated by the image below.
As you can see above, proportional adults are usually about 8 head lengths tall. Babies are proportionally about 4 head lengths tall. They are DIFFERENT SHAPES. This is why you can’t just grade a 6m size pattern up to fit a 6 year old child – even if you go in steps as described above, you need a totally different shape, not just a larger size. The same applies in reverse. (Side note – this is also why my children’s patterns are for 18m-8. If I went beyond those measurements on either end, instead of creating two drafts I’d now be creating at least 3).
Similarly, a petite woman is a different shape than a misses regular, and that’s a different shape than women’s plus sizes. You need a new draft, not to grade up or down. Now, can you make a regular pattern work for you as a plus or petite size? Maybe. You’ll want to compare your measurements to the pattern and slash and spread or slash and overlap, but realize that you may have to do a lot of blending around the edges. And your pattern will not end up the same shape as the original pattern, so you can’t check your grading by checking the corners, and you WILL have to make a muslin to check fit. Often this is easier if you’re petite, as you can just shorten the pattern vertically by more than the 3/8″ per size (but not more than 1-2″ at a time). With plus sizes it gets trickier, especially depending on where you carry your weight. The same volume of woman can come in a lot of different shaped containers. So measure, measure, measure, and use inexpensive fabric to muslin. And once you get a muslin that fits, SAVE IT. That baby is gold and a great starting point for pattern modifications next time you find a pattern you want to try that doesn’t come in your size.
Pants and sleeves are shown below. As you grade these items, keep in mind that the top of pants will get spread more than the bottom (our hips and thighs grow wider faster than our ankles) and that the cap of a sleeve has to increase in proportion to the bodice it’s going to fit. (Not sure about some of this pattern vocabulary? Check this post).
This post raised a few questions so I decided to write a part 2 – see it here.
For more in depth grading, including how I use a computer to speed things up, I offer this course. This is aimed at those who want to sell their patterns, and includes a lot more specifics, examples, video and math worksheets and computer shortcuts for you to figure out your own grade rules and grade patterns you plan to sell.
For more help just grading patterns for yourself, this article is a great resource.Get access to my free pattern gallery - sign up for my newsletter!