The most commonly reported microstructural measure in literature is the average grain size. In addition to measurement of average grain size, other material specific factors such as differences in phase structure and grain size distribution need to be considered. For heterogeneous materials such as welded low-alloy steel joints, the grain size distribution is of particular interest since it has been shown to influence the mechanical properties. Improved grain size measurement methods are thus required to enhance the understanding between grain size distribution and mechanical properties. This code is an implementation of the line-sampled and point-sampled linear intercept length methods published in Refs. [1-2], utilising the functionalities of the open-source toolbox MTEX. The code measures the average grain size, relative grain size dispersion, and the volume-weighted average grain size. In addition, the spatial grain size variation is visualized and moving averages of the grain size are calculated in horizontal and vertical directions. For more details, refer to the two publications [1-2], the supplementary dataset [3] and WIKI page [4] given below. Installation Download MTEX, the current code is developed with MTEX version 5.6 (Also works with e.g. MTEX 5.3, but requires a bugfix for intersect.m) In MATLAB navigate to the path of MTEX, and execute command "install_mtex" Open intercept_length_v3a_MTEX.m Import EBSD data as variable named 'ebsd'. Example data can be loaded using e.g. the command 'mtexdata csl;' Check the parameters set at sections 'Linear intercept parameters' and 'EBSD processing parameters'. Typical parameters are set as default. Run the code (F5). For statistical analysis use the distribution fitting toolbox 'dfittool', refer to the the 'List of output variables' below. Required matlab files: For MTEX versions earlier than 5.6, a bugfix is required for the MTEX file 'intersect.m'.a bugfix is. See https://github.com/mtex-toolbox/mtex/issues/415 for issue description and https://github.com/mtex-toolbox/mtex/tree/develop/EBSDAnalysis/%40grainBoundary for the fixed 'intersect.m' file. Published under GNU GPL v3 License. For further information, refer to the following articles and the Wiki page: [1] Materials Science and Engineering: A, 2014; 592: 28-39, http://dx.doi.org/10.1016/j.msea.2013.10.094 [2] Welding in the World. 2016; 60: 673-678. http://dx.doi.org/10.1007/s40194-016-0318-8 [3] Supplementary datasets for welded low-alloy steels: http://dx.doi.org/10.5281/zenodo.5054204 [4] Aalto University Wiki - https://wiki.aalto.fi/display/GSMUM The work is related to International Institute of Welding Commission C-IX, document nr. IX-L-1239-2021. Related journal article has been published in Welding in the World: https://doi.org/10.1007/s40194-021-01225-w Revision history: v3a MTEX: First public version.