How many grams make up a yard?

Answer 1

It depends on the weight of the fiber used to make the yarn. Very fine spun, light-weight fiber, such as mohair, weighs less than very heavy, thickly spun fiber such as recycled sari silk.

The only real way to be absolutely certain is to weigh a yard of the yarn. A mostly accurate (and easier) way is to read the yarn label. The label should list how many yards/metres there are per 50 or 100 grams, e.g., "200yds/100g". Then just do the math.