Refractive Index of BK7, Float Glass

BK7 is a ubiquitous moderate-refractive-index glass. The designation "BK7" originates with Schott AG: B indicates a borosilicate glass, while K comes from the German krone (= crown) as this is also referred to as a crown glass. Borosilicate glasses are produced from alkali-lime silicates containing approximately 10% boric oxide. Because BK7 has been available for years, its refractive indices, index dispersion, Abbe number, and other properties have been well-characterized. While it does have many desirable properties, it is typically replaced by fused silica when transparency below 320nm is desired.

For a typical sample of BK7 the refractive index and extinction coefficient at 632.8 nm are 1.515 and 0.000. Below are files of complete refractive index and extinction coefficients. If the file is not available for download, you can request our proprietary file by clicking "Request".

  • Tab-delimited data file for unrestricted use
Wavelength (nm)

Refractive Index Reference - From transmittance spectrum of 200 micron thick sample

No guarantee of accuracy - use at your own risk.