Sherwoods give weight, composition and suggestions for making up. Empress Mills give weights.
From experience of trying to find jeans denim, I would say weight below 8oz is lightweight, 8-14 is medium weight and anything higher is heavyweight. I would buy 8-10 for jeans, skirts and jackets. I did find a website that gave an explanation, but can't find it now....typical.
I would suggest either emailing and asking the seller the weight and what they would recommend the fabric to be made up as, or get a sample. Jeans fabric has now become much softer and is often washed and treated. For those old enough, remember the Wrangler and Levi jeans of the 70's that could stand up on their own