The GSM formula (Grams per Square Meter) is a standard calculation used to determine the weight of materials like paper, fabric, and cardboard. It helps in measuring the thickness and quality of these materials. The formula involves dividing the weight of a sample by its area and multiplying by 10,000 for consistency. Industries like packaging and textiles use the GSM formula to ensure product durability and compliance with quality standards, making it a vital tool for testing.