GSM and poundage are two different ways to measure the weight of paper, and they are commonly used in different parts of the world.

GSM stands for grams per square metre, and it is a metric measurement of paper weight. It represents the weight of one square meter of paper in grams. For example, a 100 GSM paper would weigh 100 grams per square metre.

Poundage, on the other hand, is a measurement of paper weight that is commonly used in the USA and UK. It represents the weight of 500 sheets of paper (a ream) in pounds. So 300gsm watercolour paper in 56x76 size is 140lb – this is the weight of 500sheets of that size.

The weight of paper does not always determine its thickness or quality. Two papers with the same weight can have different thicknesses or textures depending on factors such as the type of fibre used, and the type of pressing.Hot pressed papers are generally thinner for the same weight.

When selecting paper for a specific purpose, it is important to consider both the weight and other factors such as thickness, texture, foldability, and finish to ensure that the paper will meet the requirements of the project.