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 1.51502 and 4.092389E-07. 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".

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

No guarantee of accuracy - use at your own risk.

Tab-delimited data file for unrestricted use: