The last few years have seen the proliferation of measures that quantify the scientific output of researchers. Yet, most of these measures focus on productivity, thus fostering the "publish or perish" paradigm. This article proposes a measure that aims at quantifying the impact of research de-emphasizing productivity, thus providing scientists an alternative, conceivably fairer, evaluation of their work. The measure builds from a published manuscript, the literature's most basic building block. The impact of an article is defined as the number of lead authors that have been influenced by it. Thus, the measure aims at quantifying the manuscript's reach, putting emphasis on scientists rather than on raw citations. The measure is then extrapolated to researchers and institutions.