How much yarn do you need for a Long Tail Cast On?

5 easy ways you need to calculate how much yarn for a long tail cast on you will need. How to measure, estimate or calculate yarn requirements.

Have you ever run out of yarn after casting on 50+ stitches? I certainly have. While the long tail cast on is fast to knit nobody likes to waste time casting on a second time, eh? In this tutorial, I’m going to show you 5 easy methods to find out how much yarn to use for a long tail cast on.

New knitters might wonder: Well, what’s the big deal? For a scarf or a potholder, you might need to cast on only a couple of stitches. Pulling out a yard and cutting off the rest usually works out just fine. But when you start your first shawl and you need to cast on 200+ stitches, things suddenly change dramatically. Sometimes, you are also working with expensive yarn or you only got a couple of yards left, so you really don’t want to waste too much yarn.

But fear not, I compiled a couple of easy methods to calculate how much yarn is needed for a long tail cast on for every knitter. Some require maths, others some extra work. And the best part. They also work for the German Twisted cast on.

So, let’s dive right into it, eh?

Note: Check out this tutorial with 2 other easy cast-on techniques for beginners.

#1 The Rule of thumb method

Estimating the length of yarn needed for a long tail cast on

If you got a short work, with only a couple of stitches to knit, then a simple rule of thumb will help you out. Simply set aside 4 times as much yarn as your final work will be wide. So, if you want to knit a scarf that is 10 inches wide, set aside 40 inches. This will leave a little tail long enough for weaving in later on.

For bigger works, you should change it to 3 times and 10 percent for the extra tail. But I personally don’t feel this is the best method for larger projects. But if you are just started to learn knitting, this method will be great! Of course, you will need a ruler or a tape, but for measuring out shorter lengths of yarn, I feel it’s easy to do.

There are two problems with this method: If you are knitting a pattern, you probably won’t know how wide it will be (except you do some math with a swatch).

Also, sometimes you cast on around two needles or even use the 2-needle cast on. In these cases, it’s better to calculate with the factor 5 times as a stretchier edge will require even more yarn.

#2 Wrap method

Wrapping the yarn around the needle to see how much yarn to use for a long tail cast on

The second easy method to determine how to measure the yarn needed for a long tail cast on is the wrapping method. It’s quite simple. Take your needle, start with the very end of your yarn, and wrap the yarn around as many times as the stitch count of your pattern. So, if your pattern requires you to cast on 50 stitches, wrap the yarn around the needle 50 times.

Unravel it again, and that’s how much yarn you will need for the long tail cast on. Make sure to leave a little extra tail for weaving in. Also, you have to wrap the yarn around your needle with an even tension – otherwise you end up with too little or too much.

Again, this method is great for beginners and smaller projects. I wouldn’t trust it too much if you are knitting a large shawl – especially as this method won’t work on circular needles (the cable is much thinner than your needle).

#3 Zig-Zag Method

Using the zig zag method to measure out the yarn requirements for a long tail cast on

The most reliable method to find out how much yarn to use for a long tail cast on is the zig-zag method. You simply cast on 10 stitches, unravel it, measure how much yarn you needed, and then measure out as many additional lengths as your pattern requires.

So, if your knitting project asks for 50 stitches, you have to measure out 4 additional lengths. Leave a generous tail to weave in and you’ll be fine.

Simply arrange the yarn on your kitchen table or the floor and try to keep all lines even so you don’t end up with too much or too little yarn in the end. Use the initial length as a gauge – no need to actually measure things out. If you want to make extra sure, you can of course also measure things with proper tape.

What I like about this method is:

  • It requires no ruler
  • is extremely accurate
  • almost no mathematics is involved
  • can be applied to every needle & yarn

#4 Two strands method

Using the double stranded long tail cast on so you don't need to guess how much yarn you will need

A method that does not involve and calculation or guesswork is the two strands cast on method. Instead of casting your stitches from the tail, you are using a separate yarn. This can be a different color or the other end of your yarn (only possible if you are working with yarn cakes or skeins that are wrapped in a way you can access both ends).

This is how it works:

Step 1: First, make a slip knot using BOTH yarns.

Step 2: Cast on as many stitches as you need but remember to keep the future working yarn around your index finger and the “tail yarn” around your thumbs. Now, cast on one more stitch. So, if your pattern requires 20 stitches, cast on 21.

Step 3: Knit the first row. The last stitch will be your double slip knot. You won’t knit this one. Instead, slip it, and unravel it. Turn the work and continue knitting according to your pattern.

Step 4: You can now cut off the tail yarn.

I personally don’t like this method because it requires you to weave in two strands. Also, I love knitting from a ball held in a yarn holder and this method won’t work that way – unless you want a two-colored edge or you got another ball in the same color (typically you will have that for larger projects, though).

On a more positive note, you will never run out of yarn with this method and you won’t have a knot in your cast on edge.

Stitches per Inch

Counting the stitches per inch to find out how much yarn to cast on
Yarn weightStitches per inch

There are quite a lot of charts out there that tell you the stitches per inch for the most common yarn weights. Some yarn labels even give you the same information. You can use this information to calculate the yarn you need for your long tail cast on. So, if your yarn has 4 stitches per inch, and you need 40 stitches, well then you’ll need to set aside a tail of 10 inches + a little extra.

I’m not going to recommend these cheat sheets here because I think this method is totally unreliable. The stitch count varies so much depending on your needle size and yarn material (wool, cotton, and alpaca do knit differently). At best, you end up with a guestimation. So, you end up throwing away extra yarn to be on the safe side. (Note: You could measure out your swatch, if you knitted one, though.)

Also, you will need to do quite some calculation and measure out correctly – this can be annoyingly hard if you don’t have a big enough ruler or tape. What I mean is, if the stitch count is 7 per inch, but you need 155 stitches, then you probably need a calculator. Most mobile phones have one now, but it just adds to the complexity. If it was a foolproof and exact method, I’d say it was worth it – but since it’s just a hunch of a guess…

Note: Stitches per inch has nothing to do with wraps per inch.

Further things to consider when you want to know how much yarn you need for a long tail cast on

Last, but not least, I wanted to share a little secret: I personally never use one of the methods above. I don’t. I just pull out some extra yarn and cut away the rest. After having knitted so many projects in my life, I seem to know how much yarn I need for the long-tail cast-on on a subconscious level. In 98% of all cases, I get it right on the first try – with a tail of 10 inches or less. And I bet, this will work in your favor after some time as well.

That being said, I frequently lose track of how many stitches I cast on and will have to recount like 10 times. I usually count in batches of 10, make a little note, and then cast on another 10 – but I still fail. lol. This is especially hard if I am alternating knit and purl cast on stitches for a rib pattern (like in socks). Then I lose track of both how many stitches I already cast on AND if my next should be a purl or a knit (or where I did go wrong). And that’s when I have to unravel and try again.

I really want to stress that it’s no problem to cast on twice. It really isn’t. What is more important is that you get it right and neat. The edge will often be the most visible part of your work. Take your time, plan things properly and go slow!

Related article:

So, this was my little guide to finding out how much yarn to use for a long tail cast on. I hope I was able to help you. Make sure to comment which method you like best.

11 thoughts on “How much yarn do you need for a Long Tail Cast On?”

  1. Norman – You’re brain is like mine = the most reliable way seems to be the ‘zig-zag’ method – small amt of time to cast on 10 sts, then multiply it out in a VISIBLE manner. That is so easy & straightforward. HOORAY – thank you so much. Marga

      • Your tips are invaluable. I have one that most people can use but rarely notice.

        If you have a printed pattern beside you as you are starting to cast on, note that the paper is 11-1/2 in. (A4 is 11-3/4 in). You can use the zig-zag method without having your tape measure with you. If you need a lot of length, use a yardstick and it is three times quicker.

        • Hey Mariyln,
          that’s a cool knitting hack! Never thought of it (probably cuz I always have a tape in my project bag, lol). Still smart thinking really!

  2. Does the amount of yarn used for the cast on differ based on holding the tail over the thumb or over the index finger? With the methods shown above, is there a set direction to place the tail?


    • Well, for a standard continental longtail cast-on, the tail should always be wrapped around your thumb. So I am not sure I understand I understand your question.

  3. Hi Norm,. I am pretty much a beginner, lots of scarfs. My current project is a shawl using #4 yarn on 15mm needles. When finished it should be 20in x 60in. Could you help with # of stitches to cast on? Using the zig zag method I should be able to figure out the amount of yarn needed for long tail cast on.

  4. If I cast on a number of stitches I place markers every 15 or 20 cast ons.. I have certainly had to undo stitches because tail way too long. For me wrapping the needle works well.

    • I do something similar, Susan, only I place markers every 10 stitches when casting on. As a new knitter, I think it saves me time, not needing to count as many stitches to double-check whether I have the right amount.

  5. I am still relatively new to knitting. I have knitted a test potholder before but forgot how I did it. I am trying to knit another potholder with 100% cotton yarn (Cascade Yarns Ultra Pima). It is DK/8ply weight yarn. 220 yds (200 m) Worth. 1 skein. I am trying to use two #6 size straight knitting needles. The pattern I am working with calls for 24 cast on stitches with a 6 inch tail left over for 1 potholder. How many inches of yarn would I need to measure out using a long tail cast on method?


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