In the music industry, the top 40 is the current, forty most-popular songs in a particular genre. It is the best-selling or most frequently broadcast popular music. Record charts have traditionally consisted of a total of 40 songs. "Top 40" or " contemporary hit radio " is also a radio format.
According to producer Richard Fatherley, Todd Storz was the inventor of the format, at his radio station KOWH in Omaha, Nebraska.  Storz used what he saw from the repetition of plays on the jukebox to develop his platform. The format was commercially successful, and Storz and his father Robert, under the name of the Storz Broadcasting Company, subsequently acquired other stations to use the new Top 40 format. In 1989 Todd Storz was inducted into the Nebraska Broadcasters Association Hall of Fame. 
The term "Top 40" for a radio format appeared in 1960. The Top 40, whether surveyed by a radio station or a publication, was a list of songs that shared only the common characteristic of being newly released. Its introduction coincided with a transition from the old ten-inch 78 rpm record format for single "pop" recordings to the seven-inch vinyl 45 rpm format, introduced in 1949, which was outselling it by 1954 and soon replaced it completely in 1958. The Top 40 thereafter became a survey of the popularity of 45 rpm singles and their airplay on the radio. Some nationally syndicated radio shows, such as American Top 40 , featured a countdown of the 40 highest ranked songs on a particular music or entertainment publication. Although such publications often listed more than 40 charted hits, such as the Billboard Hot 100, time constraints allowed for the airing of only 40 songs; hence, the term "top 40" gradually became part of the vernacular associated with popular music.
From the 1980s onwards, different recording formats have competed with the 45rpm vinyl record such as cassette -singles, CD singles, digital downloads and streaming. Many music charts changed their eligibility rules to incorporate some or all of these.
Top 40 music charts and programs
The following run charts or programs consisting a total of 40 tracks:
|American Top 40||radio airplay countdown|
|Ö3 Austria Top 40||airplay + sales chart|
|Dutch Top 40||airplay + streaming and social media trends|
|Los 40 Principales||Spanish chart|
|Take 40 Australia||Australian top 40 countdown|
|The Official Chart||UK sales + streaming chart on BBC Radio 1|
|The Net 40||a worldwide user generated Top 40 show|