MITCalc - Mechanical, Industrial and Technical Calculations for many CAD systems
Multi-language mechanical and technical calculation package includes solutions for gear, belt and chain drives, bearings, springs, beam, shaft, bolt connection, shaft connection, tolerances and many others. The calculations are compatible with many types of 2D and 3D CAD systems (AutoCAD, AutoCAD LT, IntelliCAD, TurboCAD, Autodesk Inventor, SolidWorks, SolidEdge, Pro/ENGINEER) and support both Imperial and Metric units and are processed according to ANSI, ISO, DIN, BS, Japanese and other standards.
https://www.mitcalc.com/