Words like Grammage (GSM), basis weight, caliper (thickness), bulk, density  are different meaning, were caliper of paper is said in micron 1/1000  of mm or point/mils 1/1000 of inch according to scale we use. On the other side grammage GSM (g/m²) of paper measured with weighing scale , square meter of paper is taken and weighed in this type of scale now a days digital scales are available. Basis weight usually pack of 500 sheets on standard size measured in pound (lb) were paper available in ream (uncut) those days. Density of paper is grammage by thickness as kg/m² in unit, were as bulk multiply grammage and thickness with 1000 unit is cm^3/g.

Commonly word basis weight is compared with GSM, were now a days paper are supplied in reels. We have tried our hands with formulas that help us to find things easier.