You asked the Evangelicals how many there are. I asked adherents.com.
http://www.adherents.com/misc/BarnaPoll.html
Evangelicals Are Scarce
All Barna Research studies define "evangelicals" as individuals who meet the born again criteria; say their faith is very important in their life today; believe they have a personal responsibility to share their religious beliefs about Christ with non-Christians; acknowledge the existence of Satan; contend that eternal salvation is possible only through God's grace, not through good deeds; believe that Jesus Christ lived a sinless life on earth; and describe God as the all-knowing, all-powerful, perfect deity who created the universe and still rules it today. In this approach, being classified as an evangelical has no relationship to church affiliation or attendance, nor does it rely upon people describing themselves as "evangelical."
This classification model indicates that
only 8% of adults are evangelicals. Barna Research data show that 12% of adults were evangelicals a decade ago, but
the number has dropped by a third as Americans continue to reshape their theological views.
Not surprisingly, there were only three denominations that had at least one-quarter of their adherents qualify as evangelicals: the Assemblies of God (33%), non-denominational Protestant (29%), and Pentecostal (27%) churches. One out of every seven Baptists (14%) met the evangelical classification. An unexpectedly high proportion of people associated with the Churches of Christ - 12% - fit this standard. (Barna explained that this was because a majority of the category was comprised of individuals associated with congregations not part of the United Church of Christ cluster, which tends to have very liberal interpretations of Scripture.) Churches that have the lowest proportion of adherents meeting the evangelical criteria were the Catholic, Episcopal, and Mormon churches, each of which has just 1% of its people in this category.