Evangelical Protestants garner much attention in polling and public opinion research, in large part because they have become an important electoral coalition in conservative politics. Despite this attention, measuring white evangelicals remains elusive and often opaque. This article seeks to provide practical guidance to researchers who want to measure or analyze evangelicals. In the social sciences, many have adopted a detailed religious affiliation approach that categorizes evangelicals based on the religious tradition of the denominations to which they belong. Others have used a simpler self-identification classification scheme, which asks respondents if they consider themselves “born-again or evangelical”, though it is often unclear if these pollsters and researchers limit their evangelical classification to Protestant self-identifiers. While the affiliation and self-identification schemes are predominant, a practical examination of which approach is best for researchers has been absent until now. Using several waves of the General Social Survey and the Cooperative Congressional Election Study, we compare the affiliation and self-identification approaches to classifying evangelicals. We find almost no statistical differences between the two measurements in prominent demographic, political, or religious factors. Thus, we suggest that for most researchers, especially when space and time are important considerations, a simple question about broad religious affiliation followed by a born-again or evangelical self-identification question will suffice.