This part of the program package ECOWEIGHT contains a program for the calculation of economic weights for dairy as well as non-dairy sheep. The program was written on the basis of a bio-economic model for a sheep production systems with one lambing per year. The model simulates the life-cycle production of a ewe flock and the growth performance of offspring in rearing and fattening. The Markov chain approach was used to simulate flock dynamics. The program calculates the structure of the production system in its stationary state, the economic efficiency of the system expressed as a function of biological traits of animals and of management and economic parameters. In comparison with the version for sheep 4.1.1. published in 2008, in the 5th version considerable changes and improvements have been made. The program simulates production systems with pure-breeding as well as cross-breeding and allows the calculation of economic weights for any breeds involved in crossing. The economic weights can be applied in breeding programmes for different sheep breeds. The program is written in C, the source code and compiled versions for Windows and LINUX are made available as freeware.