Question: How do they determine the weight?
Answer: The weight refers to how much a yard of fabric weighs. A yard of 14 oz. denim weighs 14oz.
Question: I've seen denim listed from 5 oz to 20 oz. How do I know what to buy without touching it.
Answer:The swatches shown here are from fabric.com. Each swatch is labeled with the fabric information, fiber contents, care instructions and the width. Almost all online retailers offer fabric swatches.