The Brinell hardness number (BHN) is a measure of a material's hardness, specifically metals. It is determined by pressing a hard steel or carbide ball into the surface of the material under a specific load. The diameter of the indentation left in the material is then measured, and the BHN is calculated using the load and the indentation size. This method is particularly useful for materials with a coarse or uneven structure, such as castings and forgings. The BHN provides valuable information for engineers and manufacturers when selecting materials for various applications, ensuring they meet required strength and durability standards.