Choosing the size to knit when you have gauge differences and size variations can be a challenge.
Most knitters realize early on in their knitting life that the basic building block of knitting is gauge and that gauge does not always work out in nice even whole numbers. For many years, I knit things mainly for myself, of my own invention and was most concerned with getting good fit on my body. If the fabric I created had a gauge that was not a whole, half number or quarter number, I didn't worry about it. I just went with my gauge what ever it was, and multiplied by the number of inches of knitting required. I would adjust stitch numbers according to my stitch pattern and go with the number closest to my target stitch total. I also always add in selvage stitches, that are not included in my target number, to be as accurate as possible. Gauge swatches are normally worked in 4 inches so they partially guarantee the usual gauge increments. If you seem to have problems with sizing I recommend that you create larger swatches for more accurate numbers. Simply divide the number of stitches in for example 6 inches or 9 inches down to the 1 inch total.
Small differences in gauge can equal large size variations and it is best to be aware of this. Let's say you are aiming for 22 stitches over 4 inches and you get 21.5. Changing needle sizes might get you 22.5 stitches instead of the elusive 22. The former gives you a per inch gauge of 5.375 and the latter gives you 5.625. On a 40 inch sweater this equates to stitch counts of 215 vs. 225, before you add in seaming stitches. Depending on the ease already accounted for this could change the overall fit considerably but more importantly it could make the garment very different from the one the knitter intended to make. As the sizes are graded up and down, gauge makes a smaller difference on the smaller sizes and a larger difference on the largest sizes. The different gauges could also create a fabric with either more or less drape. Keep in mind that people also do not always measure in whole numbers, only patterns do. We pick our pattern size from a range that is usually in whole numbers and may jump sizes in 2 inch or even larger increments. In a garment with a back and a front created in 2 pieces you will lose 4 stitches to seaming, if your gauge is 4 stitches per inch you just lost an inch of ease sewing it up.
Add to all of this the fact that ease preferences vary widely among knitters and designers. You should also know that ease requirements get larger as fabric gets thicker and as it stretches less.
The possible permutations can make my head spin! Designers have to pick a size, work with the numbers and write the pattern that way because we have to start somewhere. However the knitter does have the option of modifying or just knitting a different size to customize to their own measurements, ease preferences and gauge variations.
I often helped customers with this when I worked in my LYS. The steps to follow once you have done your gauge swatch are below:
If you have matched gauge exactly:
- Measure your own bust.
- Measure a garment (with a similar weight fabric to the one you will be creating), that you like the fit of. The difference tells you how much ease you like which is valuable information when choosing which size to knit. Having the numbers for both step 1 and 2 help when choosing between 2 possible options of size.
- Check the pattern for the finished measurements, not the sizes, and choose the one closest to your number in step 2. Don't forget that some stitches will be lost in the seams if there are any in the chosen pattern. Do a quick calculation to be sure the stitch numbers match up to your target as well, by multiplying the one inch gauge by the measurement. It is not unusual for patterns to round measurement numbers up or down. As well the differences between imperial and metric conversions can make some small discrepancies.
If you were unable to match gauge exactly:
- Follow steps 1 and 2 above.
- Use the number that you got when you did your swatch. Multiply that number by the inches that you got in step 2.
- Check the pattern for the stitch numbers of each size, and choose the one closest to your number in step 2 by looking at the stitch totals (remembering to exclude seam stitches).
- Check lengths on the sizes as well and compare to your own measurements. You may end up knitting one size and using the length measurements from a different size.