Geometric design and strength check of internal spur gear with straight and helical toothing. Application is developed in MS Excel, is multi-language and supports Imperial and Metric units and solves the following main tasks:- Calculation of helical and straight toothing.- Automatic design of a transmission with the minimum number of input requirements.- Design for entered coefficients of safety (static, dynamic).- Calculation of complete geometric parameters (including corrected toothing).- Optimization of toothing by use of proper correction (balancing specific slips, miminizing specific slips, strength...).- Calculation of strength parameters, safety check.- Design of gearing for exact axis distance.- Complete calculation of tolerances in accordance with ISO 1328 (ANSI/AGMA 2015-1-A01)- Simple defining of the new materials according ISO 6336-5 (ANSI/AGMA 2001--D04)- Comprehensive theoretical part in the documentation.- Supplementary calculations (calculation of parameters of the existing gear, temperature rise, design of shafts,check dimensions).- Drawings of an accurate tooth shape including data (X,Y coordinates).- Support of 2D and 3D CAD systems. (AutoCAD, AutoCAD LT, IntelliCAD, Ashlar Graphite, TurboCAD, BricsCAD, ZWCAD, ProgeCAD, Autodesk Inventor, SolidWorks, SolidEdge, Creo).The calculations use procedures, algorithms and data from standards ANSI, ISO, DIN, BS and specialized literature.Used standards: ISO 6336-1:2006; ISO 6336-2:2006; ISO 6336-3:2006; ISO 6336-5:2006, ISO 1265; ISO 1328-1:1997; ISO 1328-2:1997; ISO 1122-1:1998, ANSI/AGMA 2001-D04 , AGMA 908-B89, ANSI/AGMA 2015- 1-A01, ANSI/AGMA 2015-2-A06This module is a standalone part of MITCalc - Mechanical and Technical Calculation Package for gear, belt and chain drives, springs, beam, shaft, bolt connection, shaft connection, tolerances and many others.