Finding the strength of an edge in a network has always been a big demand. In the context of social networks, it allows to estimate the relationship strength between users. The best-known method to compute edge strength is the Neighbourhood Overlap. It computes the ratio of common neighbours to all neighbours of an edge terminal nodes. This method has been initially proposed for unweighted networks and later extended for weighted ones. These two versions of the method are not mathematically equivalent: In fact, an unweighted network is commonly considered as weighted with all edge weights equal to one. Using both existent versions of Neighbourhood Overlap on such network produce completely different values. In this paper, we tackle this problem and propose a new generalization for Neighbourhood Overlap that works equally for unweighted and weighted networks. Experiment performed on networks with various parameters showed similar performance of our measure to the existing measures.