Someone on the yahoo groups knitlist asked:
i’m an advanced beginner knitter. my question is this-i understand what gauge has to do with how a knitted object might turn out, and even yardage (and how it relates to gauge). how does weight come into the picture? if yardage for 2 different types of yarn is approximately the same, but one is 50g and one is 100g, how does that affect things?
First, this is an extremely common question, particularly since the example in your question corresponds precisely to the case where a person knits two strands of yarn held together. It’s also a very good question to ask if you like to save money. Chunky yarns often cost much more than worsted weight yarns of similar quality, and you can save big bucks if you use two strands of worsted weight yarn together.
So, because it’s such a good question, I’m going to answer at length. If you are sane, and just want a simple, quick and dirty answer to how knitting yarn double stranded affects things, just scroll to the bottom of this article, and find the summary, which provides the rules of thumb which contain the mystery numbers “1.4″ and “0.7″.
If you are insanely curious and want to understand why you use the numbers 1.4 and 0.7 to convert, read the overview of one geometry principle that explains where these conversion factors .
Oversimplified Geometric Principle:
First, think of one strand of yarn as being a long flexible rod with a square cross-section as illustrated by the blue square in the figure below. Think of the other strand as a similar rod. If we add the two rods, area of two rods together is twice the area of 1 rod.
Now, suppose we mash the two rods together and reform them into a square purple rod with an area equal to the sum of the blue and red areas. How long is the side of the new square?
Remember the area of a square is equal to the square of the length of the sides. The square root of 2 happens to be equal to approximately 1.4. So, the width of the new square is approximately 1.4 times the width of the individual squares; notice I drew the purple one about that size.
Now, you are probably thinking “but the cross section of yarn looks more like a circle”.
You’re right. But, I’d get the same result if I’d used circles in my example. The diameter of the circle made by mashing two circles together is approximately 1.4 times the diameter of each individual circle. But, I won’t discuss circles because then I’d have to write a formula containing this symbol “π ” (aka, “pi” ) and then multiply and divide by that π. Interestingly, I’d get the same result if I thought the yarn looked like triangular rods, or any fairly solid looking geometric shape. (Problems arise if the yarn is fun fur.)
Anyway, I could discuss more geometry, and describe how to lay these strands across a piece of paper to figure out yardage, weigh the paper and estimate a whole bunch of stuff. But I really only wanted you to understand the number 1.4 doesn’t seem to come out of the blue.
Anyway, people who’ve been introduced to the concept of dimensional analysis know it’s unnecessary to do any more geometry problems; the only dimension in this problem is “length” and the only length scale is the yarn thickness. So, once I’ve found the conversion factor for the length of the side of the square, I’ve found the yarn conversion for, well, everything having to do with length only.
Ok now, using the magic conversion factor of 1.4 (i.e. the square root of two because we are using two strands), you can answer a few questions.
- How does gauge change when I use a yarn double stranded? If one strand of yarn knits up “nicely” at 5 stitches per inch, two strands will knit up “nicely” at (5/ 1.4) = 3.5 stitches per inch. Notice, I divided the gauge by the square root of 2, that is, by 1.4. Also, notice that 1/1.4 = 0.7. If you are in the store and trying to get a quick estimate of the stitch gauge if you double the yarn, it’s easier to multiply by 0.7 than divide by 1.4. So, most people will prefer to memorize 5 * 0.7 = 3.5 . Notice, I’ve now explained both 1.4 and 0.7? ).
- How many yards of yarn will you need if you recalculate a pattern to knit up at the new gauge? If it takes 140 yards to knit up a certain area of fabric (say 300 square inches) at 5 stitches per inch, it will take approximately 140/1.4 = 100 yards of yarn to knit the same area at 3.5 stitches per inch. So, you need less yardage of the doubled yarn.
But wait! Remember: if you double strand, the 100 yards is 100 yards after doubling the yarn. So, if you conclude you need 100 yards of the double stranded yarn, buy 200 yards of the single stranded yarn. When you double it, the strand will only be 100 yards long, right?
- How many ounces of yarn will you need to use at the new gauge? Well, if it takes 70 grams to knit a certain area (say 300 square inches) with the single stranded yarn knit at 5 st/inch, it will take 100 grams to knit the same area at 3.5 st/inch using the yarn doubled. Ok, how did I get this? Well, I took (70 / 1.4) *2 = 100! Why the two? That’s because after you double strand, the 100 yards of yarn weighs twice as much as one 100 yards of 1 strand. Oh guess what? Since 1.4 is equal to the square root of two, it would have been easier to just multiply like this: 70 *1.4=100. (Yes, I’m rounding.)
So, you can apply the rule above. If you think a bit, you’ll probably figure out that if you triple strand you multiply or divide by the square root of 3, right?
Don’t you wish you’d skipped to the summary?
Summary
Two summarize, the four rules worth memorizing are:
- If a yarn knits up at X stitches per inch when used single, it will knit up at approximately (X * 0.7) stitches per inch when used double stranded.
- If a sweater in your size requires Y grams of yarn when used single, a sweater or similar shape and size, knit at the new gauge will require (Y * 1.4) grams when used double stranded and knit at the gauge suggested in the previous bullet. You will need to rechart the sweater.
- Don’t use the formula to predict what happens with fun-fur, or novelty yarns that look a lot like fun fur.
- Be sure to knit up a swatch and verify you like to knit at the estimated gauge.
That’s it. Recently, I used the rules to estimate the stitch gauge and yardage when I knit Cascade 220 double stranded; right now, I’m knitting with Lion Brand Kitchen Cotton double stranded. Works like a charm.
So, go out and save some money and knit your chunky yarn sweaters with using worsted weight yarns double stranded!
Added July 30, 2005: People who read this article may also be interested in a calculator to estimate yardage needs when you modify a pattern to knit up at a new gauge.
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Lucia Liljegren: Copyright 2005-2007 Rights to all site content including knitting patterns, generators and haikus reserved.
Very useful post – I’ll be bookmarking this one. You go, geek!
Comment by Lynne — 3/22/2005 @ 1:05 pm
Thanks. I’m glad you liked it!
I always wonder who might use these long winded over-technical posts. Later, when I look at my logs, I always find they get lots of hits. So, there must be some peopel who want them.
Comment by lucia — 3/22/2005 @ 1:10 pm
Wow. I’m going to keep this info, as I was wondering about that question just a few days ago but never came even close to any kind of conclusion.
Nice to see you over at the Novices, by the way, I really like your posts.
Comment by Filomena — 3/24/2005 @ 6:27 am
Thanks! I like knitting novices. It’s a nice list.
I saw the question at the knitlist and then noticed a few people were finding my site using google search terms like “knitting with two strands”. So, I though, “hmmmm, enough people want to know this it’s worth posting what I’ve thought out and tested!”
Comment by lucia — 3/24/2005 @ 7:28 am
I’m in awe. I feel like I’ve just been to school.
Comment by sooner — 3/24/2005 @ 3:40 pm
Hi Sooner,
I figure if I can’t be hilariously funny like you and Bev, I can at least write “Dimensional analysis” in a knitting post!
Comment by lucia — 3/24/2005 @ 3:45 pm
THat was sexy math. I shared it with my mom who is a math teacher.
Comment by bevin — 3/25/2005 @ 6:32 pm
Thanks for this great article!
Comment by Linda — 7/30/2005 @ 12:17 pm
Your welcome!
Comment by lucia — 7/30/2005 @ 12:23 pm
Another question on this: The original pattern calls for 24 oz of wool at 3.25 st/inch. I am using another yarn that normally knits at 4.5 st/inch single strand and I am using it double to get 3.25 st/inch gauge. Do I need 24 oz of the lighter wool?
Comment by Linda — 8/16/2005 @ 2:14 pm
WoW! This is a great and useful website. Now what is the formula for the gauge of three strands of yarn?
Alice
Comment by Alice — 11/3/2005 @ 12:26 pm
Three? Well, in the formulas shown above, you will find the number “1.4″; that’s really the square root of 2. To modify for 3, you use the square root of three, which is, I believe 1.7!
TADA!
Comment by lucia — 11/3/2005 @ 12:32 pm
What about the size of the needles? Wouldn’t you be using a bigger needle size if you were using double strands? It seems like the gauge would change depending on the needle size. How do you account for this in your calculations?
Thanks!
Comment by Yarn_girl — 12/9/2005 @ 9:21 pm
Yes, you will need to use larger diameter needles to knit yarn the yarn when it’s doubled.
The calculation only:
1) estimates the new “recommended” gauge for the yarn. (Stitches are larger with two strands.) and
2) The amount of yarn you’ll need if you actually knit at the new recommended gauge.
It doesn’t recommend the new needle size to get the recommended gauge. As will all knitting projects, that varies from knitter to knitter. (When my mom and I knit the same yarn with the same needles, my stitches are much bigger. )
Strangely enough, the amount of yarn you use will only depend on the gauge you actually knit. So, the needle size doesn’t come into the calculation.
Comment by lucia — 12/10/2005 @ 10:17 am
Thank you! I just found this and it answered my question to a T. Knitters are the nicest people!
Comment by Tara — 7/28/2006 @ 1:57 pm
How do you calculate a combination of different weight yarns used in multiple strands?
I want to us double strand worsted plus one strand fingering (7 st/in) in order to achieve 2.25 st/in. Or I can use 2 strands chunky plus one fingering.
Any calculations for this?
Comment by Franceen — 8/13/2006 @ 5:17 pm
This is great information. I’ve been wanting to knit a sweater with 3 strands, where I change the color 1 strand at a time to “blend” the colors. I had no idea how to calculate the amount of yarn to buy for each color. Now I think I can do it. Thanks!
Comment by Susan — 1/26/2007 @ 2:09 pm
Actually I am glad I didn’t go straight to the summary. AN excellent article, well written and explained a joy to read for mad little scientists like me.
Comment by Susanne — 3/1/2007 @ 3:29 am
This is great information – thankyou very much! Another related question, how to I calculate the gauge if I use two differently sized strands, say one 4ply and one 8ply? Or am I just plain insane?
Comment by Yoke-Inn — 11/1/2007 @ 10:16 pm
I have Katherine Buss’s book–Big Book of Knitting and in it she talks about how to change a pattern when you are knitting with different yarn and needles. She uses a formula for this which includes square rotting of the stitch guage. I don’t understand any of it and wonder if someone could explain it to me. Thanks in advance
Comment by Marilyn Filter — 2/27/2009 @ 10:00 am
Marilyn,
This post discusses the square-root idea!
Believe it or not, the picture showing the two areas of squares really *is* the idea. If you add to strands of yarn, the areas add. to make a strand of yarn with twice the area. The yarn twists around itself– so naturally, it’s not really like adding two squares. But, the area across the strand is doubled.
After that, it’s possible to do pictures showing yarn covering areas, etc. Various square root relations pop-out for yarn lengt converstions, yarn area conversuions.
(btw– I figured this out on my own then did some test knitting. It works. For all I know, Katherine’s source of the knowledge is me. Or maybe this was common knowledge and I just re-invented the wheel. But for most yarns it works. (It might not work for fun fur. I could explain why, but basically, if it looks like normal yarn, this works.)
Comment by Lucia — 2/27/2009 @ 10:10 am
Found this great explanation by googling: knitting with two strands gauge
Thanks for taking the time to make this, it’s very useful. Now, being a linguist and definitely not a mathematician, I’m wondering what the formula would be if I wanted to go from two strands of one type of yarn to one strand of another type. In the instructions the gauge is given for two strands – and I’m not sure whether I should use one or two strands of the yarn I’ve chosen to use instead. Is there a magic formula for this too?
Comment by Anne — 3/16/2009 @ 6:36 am
I am still having trouble calculating the right amount of yarn I need. I am changing from double stranded to single strand. The pattern reads 700 g double stranded throughout. The yarn it calls for comes in 50 g balls and is 246 yard. The yarn I would like to use comes in 50 g balls and is 130 yards. In doing some math figuring total amount of yards needed- the pattern as written would be 3,444 yds of yarn. If I am using the original yarn in the pattern I believe that would be 14 balls. I come out with 26.5 or 27 balls using the yarn I chose. This seems like an enormous amount, not to mention the cost. Am I correct in figuring this?
Comment by Heather — 10/8/2009 @ 2:44 pm