Found Yarn Sale/Want to Convert to Yarn in Pattern

I know there has to be a simple way to do this. I found some bulky yarn online on sale. The yarn needle size is Size 10 with 13 sts over 4" and 54.5 yards per skein.
My vest pattern however calls for Size 13 needle with a 2.5 sts per inch over 4". I need 400 yards for my vest. Is there a way to determine how much I need to order?
Thanks so much for any suggestions!

Compare the [B]yarn[/B] gauge of the yarn in the pattern with yours. It may be the same. The gauge of yarn is more to categorize it than to define which needles to use.

Using yarn with a different gauge could very well affect the pattern size so keep that in mind, too.

If the pattern calls for a bulky (sounds like it does) then you might need about the same. It’s hard to say because of your own tension, actual thickness of the yarn, needle size, etc. You may even decide that your chosen yarn looks better knitted at more or less stitches per inch than what a label or pattern suggests.

Also depends on the pattern stitch; a lacey pattern will use less yarn than a solid garter or stockinette. Your pattern and yarn label probably refer to gauge of a solid pattern, usually stockinette, even if the actual vest itself is knit in a more open pattern.

I do a lot of sewing, and my rule of thumb when in doubt of needed yardage is to buy 10-20% more than called for. Better to have some left over than run out and not be able to match it later. But I am still a newbie knitter, so don’t know everything about yarn just yet.