My default method for casting on is the long-tail or sling-shot method. However, I have spent most of my knitting career underestimating the length of yarn needed in the long tail. For most of my projects, I have had to repeat the cast-on with a longer tail 2 or 3 times. This repetitive error led me to investigate methods for properly estimating the length of yarn needed for a long tail cast-on. I came across 3 reasonable methods that I will list in my order of preference.
- Method 1: Estimate based on the yarn needed to cast on a smaller number of stitches. For example, if I needed to cast on 140 stitches total, I would first cast on 10 stitches and then pull them out. I would then measure the amount of yarn that I needed to cast on those ten stitches. I would then multiply by 14 (140/10) to calculate the length of the yarn tail needed to cast on 140 stitches. I always allow for a few extra inches for weaving in ends.
- Method 2: Allow 1 inch of tail for every stitch you need to cast on. In my example, since I need 140 stitches, I would leave a tail 140 inches long. In my experience, the tail ends up being quite a bit longer than I need with this method.
- Method 3: Allow for a yarn tail that is 3 times the length of your finished cast-on edge. In this example, the finished object is a cowl with a circumference of 24 inches. The yarn tail would be (24 x 3) or 72 inches long. I have often ended up with a yarn tail that is too short using this method.
With the first method, you are using an estimation method that is exactly tailored for you. Because the amount of yarn used to cast on 10 stitches is slightly different for each of us, due to varying tension, method 1 will give you the length of tail that should be just right for your project. I have found that method number 1 gives me an appropriate tail length every time.