Calculating how much yarn to buy

I am starting a seamless sweater using E. Zimmerman’s knitting workshop and I can’t figure out how to calculate how much yarn I will need. the Gage is 4.5 to the inch, and the size is extra large
52 stitches around the chest. Anybody have a formula for figuring this out. Doesn’t have to be exact–I just don’t want to buy too little.

is there no indication in the pattern of how much yarn to use? it might be in ounces, grams, meters, yards, balls, skeins, etc? just knowing the gauge and finished width really doesn’t give you enough to work with, to calculate yardage, IMO.

is this an online workshop? can you link to it?

Yes there is a decent formula for figuring out how much yarn you’ll need,

1 Knit a 4" swatch and do not bind off, calculate the area (length x width)

2 Mark the last stich of the last row you worked, then rip out to the beginning of the first row after the cast on. mark that first stitch, then measure between the two points to get Total number of Inches of Yarn

3 You’ll need to the sq Area of project, in this case with a sweater, you’ll need the area of the body and sleeves, add those two numbers together.

4 Divide the Square Area of Project by the Sq. Area of Swatch, then Multiply by the Total number of Inches of Yarn, and it will be a large number. Divide by 36 for the yardage, and that will be the estimated number of yards for the project.

Hope this helps a bit.