Description: This link is to the Engineering Metrology Toolbox on the website of NIST where two excellent calculators can be found. One is for calculating the elastic compression of spheres and cylinders at point and line contact which is extremely useful for high precision dimensional measurements. The other is for calculating the index of refraction of air which is needed for interferometric length measurements. Link: Calculator - NIST Engineering Metrology Toolbox The Mitutoyo Institute of Metrology provides educational courses and on-demand resources across a wide variety of measurement related topics including basic inspection techniques, principles of dimensional metrology, calibration methods and GD&T. We can be contacted via email at, via phone at 888-MITUTOYO or 630-723-3620, or visit the Education home page. Education Home