Long tail cast ons are some of the most popular methods for starting a knitting project. And for good reason. They are versatile, relatively easy to learn for new knitters, and create a strong yet somewhat elastic edge.

However, many knitters often struggle with determining the right amount of yarn that is needed for the long tail. It’s extremely frustrating to cast on a perfectly tensioned edge, only to realize toward the end that you are running out of yarn! It’s also frustrating to waste a whole bunch of expensive yarn because of overestimating and leaving a tail that is too long. So how much yarn does a long tail cast on really require?

I’m going to go over the 3 most common methods for determining the amount of yarn needed for long tail cast ons, helping you achieve the perfect tail length every time. Some are more precise than others, and you can try them all out to see what works best for you. (#3 is my personal favourite!)

Why even bother with the long tail cast on?

There are many advantages of using a cast on that requires a long tail. Long tail cast ons are super versatile and tend to be more substantial and therefore more durable than other more low-profile or invisible cast ons.

This is partly because you are not only creating the edge, but also simultaneously creating the first row of knitting. This is another reason why many beginner knitters prefer long tail cast ons – they bypass that dreaded first row of knit or purl stitches, which can be tricky to work neatly (especially if you tend to cast on very tightly!).

The other cool thing is that there are many variations aside from the standard long tail cast on, all with different looks and properties like stretchiness.

For an all-purpose workhorse that is suitable for most projects, I like the German Twisted cast on, which incorporates an extra twist to add quite a bit more stretch as compared to the standard long tail cast on (I also think it’s more aesthetically pleasing than the standard).

The Double Start cast on creates a bar stretching across every 2 stitches, grouping the stitches into little pairs, and looks really great with 1×1 and 2×2 ribbing.

There’s also an “Alternating” version of both the Standard and the German Twisted cast ons, which allows you to create purl stitches in addition to knit stitches on that first row of knitting, by adding in a 2nd mirrored move, allowing you to neatly cast on in any ribbing or stitch pattern for an extra polished result. They are both also even more stretchy than their standard counterparts.

I truly think that expanding your cast-on arsenal is one of the best things you can do to take your knitting to the next level. It will allow you to find the perfect balance between form and function, starting every project on the right note, and achieving a polished final product that you can be proud of.

I’m slowly working on a comprehensive list of all the cast ons I can find, and am hoping to make short video tutorials on all of them, as well as comparison videos of the best cast ons for specific projects, measuring different variables, like stretchiness. It’s a work in progress. You can check out my collection of cast ons here – The Ultimate Cast On Cheat Sheet

No matter which long tail cast on you choose, they all require yarn to be measured out for the long tail, so how do you make sure you have enough yarn for the long tail cast on? There are a few strategies for avoiding this, and by using one of these methods, you can be sure you’ll never have to worry about running out of tail again.

How Long Should a Long Tail Be? 3 Simple Methods to Determine How Much Yarn You Need For The Long Tail Cast On:

1. Using the finished edge length as an estimate:

This is the quickest and most simple (but also most inacurate!) method – simply using the measurement of the finished garment edge to estimate how much tail is needed.

Usually patterns will give you a diagram, or at least written indication of different measurements of the finished item. Find the measurement of the cast on edge, and multiply that number by 3 – 4.

Example: If your finished cast on edge is going to be 10 inches long, then leave 30-40 inches of tail for completing your cast on edge.

Always add a few extra inches for weaving in the tail, and as insurance!

2. Using the number of stitches as an estimate:

This is another quick way that is a little bit more accurate than the 1st – using the number of stitches as a guide for estimating how much tail is needed.

Wrap the yarn around the needle 10 times (not too tight – you want it to be snugly wrapping around the needle, without being distorted or stretched out at all!), and then measure the length of yarn this required. Then multiply that out to the number of stitches you will cast on in total.

The formula is:

# of stitches to be cast on / 10 x length of yarn it took to wrap 10 times

Example: If your pattern calls for 50 stitches to be cast on, and it took you 5 inches of yarn to wrap around the needle 10 times, then you will need 50 / 10 x 5 = 25 inches of yarn for your long tail.

Always add a few inches for weaving in the tail and as insurance!

Additional Tip: To be even more precise when using the number of stitches as your guide, instead of simply wrapping the yarn around the needle, actually cast on 10 stitches with the long tail cast on of your choice. Then simply take the stitches out and measure how much yarn it took to do this, and use the same formula to multiply out to the length of yarn required.

3. Unlimited Tail Method – NO ESTIMATING REQUIRED:

The third method is the most foolproof (and my personal favourite) way of ensuring you have the perfect amount of yarn for your long tail cast ons.

It is literally impossible to make a mistake or run out of yarn using this method! It requires no estimating, no measuring, and no formulas, and you will have the perfect amount of yarn every time! How is this possible? By using 2 balls of yarn, or both ends of the same ball of yarn.

Simply join the two ends together with a slip knot, and hold the short tails out of the way. Now you have 2 long tails that are indeterminate in length – both attached to your ball (or balls) of working yarn. That means you cannot run out of yarn for your cast on.

Now cast on as many stitches as you require, then simply cut the yarn that was used for the tail, and continue knitting with the other end.

This is especially useful for when you need to cast on hundreds of stitches, and guarantees that you will not run out of yarn. It also guarantees that you won’t waste yarn by overestimating, since you will cut the yarn precisely where you stop casting on, just leaving yourself a tail long enough to weave in.

There is one very small drawback (if you can even call it that) to this method, which is that you will have an extra tail to weave in at the beginning of the cast on (technically it’s 2 tails where you joined the two ends together at the start of the cast on)

But I usually split 1 of them in half so that I have 3 ends that can be braided together, and weave them in as one braided strand, making it so that I only have 1 extra tail to weave in. This is a small price to pay in my opinion, to remove all of the stress of estimating the tail length, and always ensuring a perfect length!

Estimating the long tail length correctly is crucial for a successful cast on. If you underestimate, you may run out of yarn mid-cast on, leading to frustration and having to start over. On the other hand, if you overestimate, you’ll have a wasteful excess of yarn, which can be especially frustrating when using expensive or limited-edition yarn.

I hope you can use one of these 3 methods the next time you go to cast on a new project, so that you can have a perfect, seamless start and help you get to the the fun part quicker- knitting that cozy sweater, colourful pair of socks, or intricate lace shawl!

If you have any questions, comment below and I’d be happy to help 🙂 Good luck!