Thousands of beer lovers celebrated the 189th start of Oktoberfest, the world's largest folk festival, as Munich Mayor Dieter Reiter inserted the tap into the first keg of beer on Saturday.

If you're thinking about purchasing a keg for your next big gathering, it's important to know just how long all of that beer will last. Let's investigate.

Oktoberfest has opened in Munich after the ceremonial beer keg-tapping. Mayor Dieter Reiter officially started the 189th Oktoberfest at noon when he inserted the tap into the first keg.