First, take a look at my personal body schematic. The measurements are on a graphic below, but I want to show you the silhouette of my body. Before we go further, let me point out that I'm not shaped like most people. I have a complicated body shape-wise and have to do complicated shaping to accommodate it. Getting a correct fit for most of you will require far less effort.
So what do you do after you have this body schematic? You then figure out how much ease you want in your sweater. Ease, as you likely know, is a matter of great debate and personal preference. After a lot of trial and error, I've discovered that I prefer two inches at my bustline and four at my waist and hips. YOUR MILEAGE MAY VARY.
Some knitters (especially skinny ones) prefer zero ease or even negative ease, especially at the upper bust. In my humble opinion, this works fine for women who don't have curves (aka lumps, bumps, sags, and the like). I think larger bodies need more ease. As Dottie, my knitting pal and long-time Knitting at Large supporter, pointed out, ease should exponentially increase as the body increases. Let me explain. Assume that a 36-inch sweater includes two inches of ease, or a ratio of .05 (2 divided by 36 is .05). The way most patterns are written, the ease for a 56-inch size will be two inches, too. Dottie and I contend, however, that the ease on a 56-inch sweater should instead be the same ratio (.05 in this case) rather than the same measurement. Therefore, the ease for the larger size should be 2.8 inches (56 multiplied by .05 equals 2.8). I would then round up to three inches.
Below you'll see my optimal sweater schematic based on my ease preferences. You can see my body in light turquoise and the shape of the sweater around it. Welcome to my holy grail. This image provides a road map for every single thing I'll ever make. Of course, I need a back and a sleeve to go along with it, so I've posted them below, too.
There are a variety of reasons why you should undertake a similar task. First, you never have to measure again (unless you gain or lose weight). Second, you eliminate mystery from your knitting; you no longer need to worry about whether a sleeve is too long or a sweater is too short. With this accurate road map, you know EXACTLY how wide or long a particular sweater section needs to be.
Best of all, you can now knit almost anything to fit you, within reason anyway. I have a 60-inch finished bust size and I'm comfortable looking at sweaters that are at least 50 inches because I know which adjustments I'll need to make. As an example, take the Ravine pullover I'm going to make for the Knit Picks KAL (the schematic is shown below). The numbers in black show the measurements for the largest size, which is 52 inches. The measurements in red show the measurements I need to use to make the sweater fit me.
I want to point out a couple of things. First, note that the bust, waist, and hip measurements are significantly larger than what is provided in the pattern. That makes sense - I'm making a bigger garment. But there are some measurements that are identical - the sleeve depth, for example - and some which are smaller, such as the sleeve length. I've told you 400 times that sizes don't matter and this schematic shows exactly why. It doesn't matter what the uber-talented Glenna C says in terms of sizing. I can keep her beautiful design and make the sweater fit me, too.
Observant readers of this post will note that my back and front sweater schematics above are not identical. I'll explain this next time, and then we'll discuss how to take your optimal sweater schematic and turn it into an actual sweater.