Basis Weight

Basis Weight is a key physical indicator for sheet materials such as paper, paperboard, nonwovens, and films. It refers to the mass per unit area, commonly expressed in grams per square meter (g/m² or gsm) and pounds per ream (lb/ream). In foreign trade, basis weight directly determines material thickness, strength, cost, and application, and is a core specification in contracts, letters of credit, and quality inspection certificates. Usage scenarios include: quotations, order specifications, pre-shipment inspection, and claim basis. Precautions: Different countries may use different units (e.g., the US uses lb/ream, China uses g/m²), so conversion must be careful; basis weight is different from 'thickness'—thickness is a physical dimension, while basis weight is areal density; it is often confused with 'grammage,' but grammage leans more toward domestic standards. Difference from 'gram weight': gram weight is one expression of basis weight, but basis weight emphasizes standard test conditions (e.g., temperature and humidity equilibrium). Foreign trade practitioners should clarify the test standard in the contract (e.g., TAPPI T410, ISO 536) to avoid disputes caused by differences in test methods.