This part of the program package ECOWEIGHT contains two programs for the calculation of economic weights for beef and dairy cattle. In comparison with the 2nd version published in 2005, in the 4th version considerable changes and improvements documentedin Appendix C in the Manual have been made especially in the program for dairy cattle. The programs simulate a large range of production systems so that they can be applied nearly to all cattle breeding programmes. The programs are written in C, the source code and compiled versions for Windows and LINUX are made available as freeware.