A Guide to Relative Cost
March 15, 2026 · Morgan Trexler
Optical glass manufacturers, such as Schott, CDGM, Ohara, and others, offer many different kinds of glass, but the complexity, melt frequency, demand, and materials create a wide range of costs. To help optical designers understand the trade-offs between cost and performance, manufacturers often provide a value, Relative Cost, that captures the cost of a glass normalized to a standard, typically N-BK7 or an equivalent.
For example, Schott N-BK7 has a relative cost of 1.0, indicating it is equivalent in price to the standard (because it is the standard). By comparison, N-SF5 has a relative cost of 1.4, meaning that if a certain amount of N-BK7 costs \$100, then an equivalent amount of N-SF5 would likely cost around \$140.
While bulk material cost is important, be careful not to let bulk glass cost entirely drive pricing design decisions. Often, lens count, lens form, material grindability, tolerances, and other factors have a greater impact on cost. In high-volume optics, moldability is often a primary cost driver for the optical design.
Try using AbbeTrex's design tools to optimize glass selection based on other cost drivers, such as moldability.