How many litres of beer are drunk at Oktoberfest?

How to get close to this number

Multiply visitors by servings. The explanation gives the attendance at around six million over sixteen days, and the festival serves beer in one-litre measures. If the average visitor has one or two, the total lands in the millions of litres — and roughly one litre per visitor is exactly what the arithmetic produces.

That average is lower than people expect, and the reason is that attendance counts everyone through the gates: families, children, people eating rather than drinking, and visitors attending briefly. Event consumption averages are always dragged down by the large fraction of attendees who barely participate in the thing the event is famous for.

The regulation in the explanation is the genuinely interesting part. Only six breweries may serve, and the beer must be brewed within the city limits — a protected designation enforced by the city rather than by national or European law. The scale of the event is enormous and the supply side is deliberately tiny, which is an unusual combination in modern food and drink.