One menu lists a small glass for €3.00, another a half litre for €6.50. Which is cheaper? You can't tell without doing the maths.
The glasses
In the Netherlands beer comes in all sizes: a small 'fluitje' of 20 or 22 cl, a regular glass of 25 cl, a 33 cl bottle of specialty beer and a half litre. Menus don't always say how much is in the glass, and then you're comparing apples with oranges.
Converting to 25 cl
That's why we convert every price to a 25 cl glass: price ÷ volume × 25. The €3.00 small glass (20 cl) then costs €3.75 per 25 cl. The €6.50 half litre costs €3.25 per 25 cl. So here the big one is cheaper per sip.
And the deal score?
In the app we don't just look at price, but at the beer itself too: a heavy specialty beer is different from a light lager. The deal score is alcohol% × (cl ÷ 25) ÷ price. The higher, the more you get for your money. If a menu lists no size, we calculate per glass and list that beer separately, so it never ends up on top unfairly.
The goal is choosing smart, not drinking more. Enjoy, drink responsibly and have a glass of water too.