Ultratop 40 singles, often just Ultratop 40, is the weekly chart of best-selling singles in Wallonia and Brussels Capital Region

Brussels

Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...

, the french-speaking parts of Belgium

Belgium

Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

. Its equivalent covering the Flanders

Flanders

Flanders is the community of the Flemings but also one of the institutions in Belgium, and a geographical region located in parts of present-day Belgium, France and the Netherlands. "Flanders" can also refer to the northern part of Belgium that contains Brussels, Bruges, Ghent and Antwerp...

 region is Ultratop 50

Ultratop 50

Ultratop 50 singles, often just Ultratop 50, is the weekly chart of fifty best-selling singles in Flanders, Belgium, and is produced and published by the Ultratop organization. The chart has existed since March 31, 1995...

. Both charts are produced and published by the Ultratop

Ultratop

Ultratop is an organization which generates and publishes the official record charts in Belgium, and it is also the name of most of those charts...

 organization. Like the UK Singles Chart

UK Singles Chart

The UK Singles Chart is compiled by The Official Charts Company on behalf of the British record-industry. The full chart contains the top selling 200 singles in the United Kingdom based upon combined record sales and download numbers, though some media outlets only list the Top 40 or the Top 75 ...

, Ultratop creates charts based on retail record sales of around 500 retail outlets and legal digital downloads. Currently GfK

GfK

The GfK Group, established in 1934 as Gesellschaft für Konsumforschung is Germany's largest market research institute, and the fourth largest market research organisation in the world, after Nielsen Company, Kantar Group, and IMS Health...

 is the market observer of the charts. The chart broadcasts on Radio Contact on Saturdays from 12:00 to 14:00. The combined number of Ultratop chart listeners on the various radio or TV stations exceeds two million every week. To celebrate the 10th anniversary of the charts in 2005, a jubilee book was published. It covered all 15,282 singles from 5,882 artists thus far.