Yarn Tail Estimator for Long Tail Cast On.
We recently came across a really helpful Yarn Tail Estimator created by Nancy Wynn. Although her information is an estimate, it will provide you with chart that will guide you through multiple scenarios to choose from based on your yarn weight and needle size. Click on this image to download Nancy's Estimator.
You should also visit her website for additional resources and videos. You can also view her video below that talks about how to do a long tail cast on without having to estimate yarn tail.