How many stitches to cast on?

What are the rules to know how many stitiches to cast on ?

I’m a lazy student and I am weak in following instructions and also because I don’t find the exact size on the patterns I find or they r nt free.

I usually use long tail cast on, but what is the usage of the long tail? Do I need to leave more than 2" of tail? Because I find anything more than 2" is troublesome while I’m knitting the whole garment

I learnt that I should round the yarn on my needle for 20 times then use at length to get four times more in order to get 80sts, but it turns out I usually leave too much yarn unused so it seems to me this method won’t work ?!?

Thanks for your sharing and time!!

In general, you need to cast on the number of sts that will give you the width that you want for your project. You find out how many sts that is by making a swatch or small test piece with your yarn and your needles in whatever stitch the pattern gauge tells you (or the st you plan to use in the project) and calculating the sts/inch. Once you’ve done that you can modify the pattern to any size you want.
It’s better to have about 6 inches of tail left from the long tail in order to easily weave in the end when the project is finished. More is good too because you can use it to seam if that’s called for.
You get better at estimating how much yarn for long tail with practice. Already, you know that you’re over estimating so you can adjust by starting with a shorter tail. You can also do long tail with 2 ends of yarn and then cut one when you finish the cast on and continue with the other as your working yarn. Or try another cast on like the knit cast on. Take a look through some of the videos online or at the top of the page. There are lots of different ways to do things in knitting.

Your stitch question has been answered so I’ll comment on long tail.

I always leave 6-8 inches of tail. I don’t have a problem with that length, but if it’s too long then I don’t like it and you can accidentally knit with it. If it ends up longer than I’m comfortable with I cut it to the size I want.

I’m pretty good at eyeballing what I need now, but occasionally I still wrap. I do it ten times and see how long it is, then count by 10’s the amount I’ll need. Then I add another length for safety.

You can also use two skeins or the inside and outside yarn to cast on. Take the two ends and knot or slip knot them together and cast on normally. When you’re done cut one of them and knit with the other.

I leave a shorter tail, like a couple inches because I use a crochet hook to weave it in rather than a tapestry needle. I find that a lot easier than threading it on a needle.