How do they determine what makes the Billboard 100?

Answer by  bnoj13 (13)

The Billboards in general are based solely on sales and popularity. So the Top 100 singles with the most sales and the most radio airplay make the Billboard 100.

Answer by  Munawer (365)

Billboard 100 is based on the sales and popularity. For example Hot 100 are the songs that have sold the most copies and attracted the most radio airplay for that particular week. Billboard also has a Hot 100 Digital categorizing the most (legal) downloads, and the Hot 100 Airplay, which is based only on radio play.