In graph theory the diameter is an important topological metric for understanding size and density of a graph. Unfortunately, the graph diameter is computationally di cult to measure for even moderately-sized graphs, insomuch that approximation algorithms are commonly used instead of exact measurements. In this paper, we present a new algorithm to measure the exact diameter of unweighted graphs using vertex programming, which is easily distributed. We also show the practical performance of the algorithm in comparison to other, widely available algorithms and implementations, as well as the unreliability in accuracy of some pseudo-diameter estimators.