In the music industry, the top 40 is the current, 40 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. Frequent variants of the Top 40 are the Top 10, Top 20, Top 30, Top 50, Top 75, Top 100 and Top 200.
According to producer Richard Fatherley, Todd Storz was the inventor of the format, at his radio station KOWH in Omaha, Nebraska. Storz invented the format in the early 1950s, using the number of times a record was played on jukeboxes to compose a weekly list for broadcast. 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", describing 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 45 rpm vinyl record. This includes cassette singles, CD singles, digital downloads and streaming. Many music charts changed their eligibility rules to incorporate some, or all, of these.
Music charts and various radio programs adopt different chart formats including Top 10, 20, 30, 40, 50, 75, 100 and 200 although radio formats usually restrict to the Top 40 wherever the chart contains more than 40 songs.
Top 40 is also adopted to a radio format called Top 40 format, spinning mainly hits appearing in the official Top 40 charts of the country in addition to some upcoming hits that are greatly expected to get into the Top 40 imminently. The format is variously known also as CHR (contemporary hit radio), contemporary hits, hit list, current hits, hit music, top 40, or pop radio.