Are all fabric bolts 60" wide? I thought there were variances.
Yes, there can be differences.
The following link has some explanations. For example, by 1/4 yard is that "quarter yard" or "fat quarter"?
https://sewsweetness.com/2011/08/sewing-back-to-school-fat-quarters-half.html
Bolts of fabric can vary (32” up to 60”) but the length is 36 inches to the yard.
For cotton, chiffon, organza, satin it’s 58/60. I’m just making it 60 for simple reasons for the math to work..
Are all fabric bolts 60” wide? I thought there were variances.”””
You are correct. There are different widths in yardage. Especially wool. Some are 60” & some are 54”. I used to do alot of sewing & I always had to recheck what yardage I would need. NOT all bolts are marked, either, I learned that MY handspan was about 8 1/2 inches, so I used that to help me make sure I didn’t screw up.