How do you calculate gsm for poly bag?

To calculate the grams per square meter (GSM) for a poly bag, first measure the weight of the bag in grams. Next, determine the surface area of the bag in square meters by multiplying its length by its width (and accounting for any additional dimensions if it's not flat). Finally, divide the weight by the surface area to get the GSM: ( \text{GSM} = \frac{\text{Weight (g)}}{\text{Area (m}^2\text{)}} ).