We have developed a new method to determine the degree of mixing for a given system. The method assumes knowledge of the locations of all or some studied particles both before and after mixing. The method is scalable and gives comparable results for systems with varying shapes and sizes of the mixing space. It can also be used to determine the mixing of only a part of the space studied. Due to the information needed, the method is best suited for simulations, but in some cases it might be possible to use it with real laboratory experiments. (C) 2009 Elsevier B.V. All rights reserved.