Blocked vs. Unblocked Gauge
One of the best parts about knitting a top-down sweater is being able to try it on as you knit. But to get accurate information out of these fit checks, you must know how your unblocked gauge compares to your blocked gauge.
Many a sweater has been lovingly knit with a great seeming fit, only to grow substantially when blocked. I have had multiple test knitters completely re-knit their sweaters for this reason. While this seems like a very scary possibility, it doesn’t mean that we need to be intimidated by gauge & blocking - rather, we must seek to understand them so that we can make sweaters that fit wonderfully!
Factors that increase the chance that your garment will grow substantially with blocking are using superwash yarns and working in ribbing patterns. This is not necessarily an issue - it just means this process is of extra importance!
Understanding Blocking & Gauge
Before knitting a sweater, our swatch can tell us how our gauge will change with blocking. Many of us (including myself!) tend to mainly pay attention to the gauge after blocking, but comparing the gauge before AND after blocking will tell us how our fabric responds to the blocking process.
(1) Measure stitch & row gauge before blocking
(2) Measure stitch & row gauge again after blocking
(3) Compare these measurements
Comparing Blocked vs. Unblocked Gauge
To compare the ratio of your gauges, divide the unblocked gauge by the blocked gauge.
Ratio = Unblocked gauge / blocked gauge
For example, for the sample of my Chione sweater, my unblocked gauge was 29 sts & 44 rows per 4” (10 cm) and my blocked gauge was 28 sts & 46 rows over the same distance.
Note: If you’re not familiar with ratios, a ratio of 1 means no change, and 1.01 is 1% growth and 0.99 is 1% shrinkage.
Stitch ratio (width) = 29 sts / 28 sts = 1.04 → 4% growth
Row ratio (length) = 44 rows / 46 rows = 0.96 → 4% shrinkage
These ratios tell how your sweater as a whole will grow (or shrink!) with blocking. These numbers told me that my sample would grow in width by 4% and shrink 4% in length when blocked. In this example, these changes are explained by the broken rib stitch pattern which has a tendency to expand widthwise.
Okay, So What?
It’s entirely up to you what to do with this information! Personally, I would say that growth/shrinkage of around 5% can be dismissed as negligible. What I mean by this is - when you try on your sweater as you knit it, you can keep in the back of your mind that it might grow/shrink a little bit with blocking, but that there will not be dramatic changes.
If either your stitch or row gauge changed by 10% or more with blocking, this will be valuable to consider during your fit checks.
Consider a scenario where your row gauge grew by 10% and you knit the body to a length of 12” (30 cm).
12” (30 cm) length * 0.10 = 1.2” (3 cm) growth
So when you block this sweater, the body will grow by 1.2” (3 cm). This could mean a sweater that you thought would be a perfect length for you is now longer than you would like.
What Can We Do About This?
In this last example, we can knit the body 1.2” (3 cm) shorter than our desired length in order to have our blocked sweater be that desired length! So instead of working the body to 12” (30 cm), we can work it to 10.8” (27 cm). Alternatively, when trying on the sweater you could work the body until you though “yeah, this looks like about an inch shorter than I want” and stop there!
If you love math and numbers, you could do loads of calculations to get everything just right. Or, if you have a more casual approach, just knowing the ratio of you blocked & unblocked gauges can shape your expectations for how blocking will affect your finished sweater.
A Few More Examples
Consider how three different growth ratios affect knitting to a length of 10 in (25cm).
If your gauge grows by 10%:
10” (25 cm) * 0.1 = 1” (2.5 cm) growth
If your gauge grows by 20%:
10” (25 cm) * 0.2 = 2” (5 cm) growth
If your gauge grows by 30%:
10” (25 cm) * 0.3 = 3” (7.5 cm) growth
Clearly, the larger your ratio, the more critical it becomes to consider the growth that will happen to your sweater when you block it!
“Work To” Length
Being instructed to work to a certain length is a very common instruction in a knitting pattern. But if your swatch grew with blocking, you will need to work to a shorter length than instructed in order to get that measurement as your finished length.
A pattern can’t tell you what length to work to in your unblocked gauge, because this is individual to each knitter! The pattern is just counting on everyone having the same blocked gauge. This is particularly important to note if you are working in superwash yarn and the pattern is written for non-superwash - it’s likely the designer’s gauge changed less with blocking than yours might.
Since we know,
Pre-blocked length * ratio = Blocked length
To calculate our pre-blocked length,
Pre-blocked length = Blocked length / ratio
For example, if the “work to” length is 8” (20 cm) and your row gauge grows by 30% when blocked:
Pre-blocked length = 8” (20 cm) / 1.3 = 6.1” (15.5 cm)
So instead of working a whole 8” (20 cm), working just 6.1” (15.5 cm) will result in a blocked sweater that has the desired length.
Swatching Tips
(1) A large swatch gives more accurate information.
I always recommend a 6” (15 cm) square swatch.
(2) Measure gauge in the swatch’s center, not including edges.
In a 6” (15 cm) square swatch, measure gauge over 4” (10 cm) in the middle of the swatch.
(3) If your sweater is worked in the round, swatch in the round.
Many knitters have a different gauge for knitting vs. purling, and this will mean that stockinette flat vs. in the round will be different as well.
Blocking Tips
(1) Block your swatch exactly as you will block your sweater.
If you have machine washable yarn and your finished sweater will go through the washer and dryer, put your swatch through the washer and dyer. If you are going to wet block your sweater and dry flat, do the same for your swatch.
(2) Only pin out your swatch if you will pin our your sweater.
I only think pinning is necessary for cables and lace, which need the extra help to relax into their final positions.
(3) Don’t trust steam blocking to tell you how your sweater will respond to washing.
If you’re making a knitted piece that will ever be washed, wet blocking is your best bet.
Moving Forward
I hope that this post has given you some valuable information about how to consider your blocked vs. unblocked gauges when working a pattern - both when trying on as you go, and when working to instructed lengths.
A beautiful part of making is understanding the process that fits best for you. Whether that’s laying out all the numbers - or using this information to help your intuition guide you - or choosing that winging it is your preferred way of working - that’s entirely up to you!
