Finding density. Each calculator above asks for a material’s density, which varies by alloy and condition — steel runs roughly 0.283 lb/in³, aluminum about 0.098 lb/in³, and brass around 0.307 lb/in³. Check the specific grade’s datasheet rather than a generic “steel” or “aluminum” figure if the part needs to hit a precise weight target.

Diameter vs. radius. The bar and tube weight formulas use radius (half the diameter) inside the squared term, so doubling a bar’s diameter roughly quadruples its weight per unit length — a mistake worth double-checking before ordering stock.

Safety factor in workholding. The workholding force calculator multiplies cutting force by a safety factor rather than using cutting force directly — a factor of 2 to 3 is a common starting point for roughing, with higher values for interrupted cuts or poor fixturing.