How many glasses does a bottle hold?

A bottle of 750 millilitres gives 7 glasses of 100 millilitres with half a glass left over, 6 glasses of 125 millilitres, or 5 glasses of 150 millilitres.

The 100 millilitre measure is not arbitrary: it is the pour that the Trimbos Institute uses for a standard glass of 12 percent wine. The sum is simple: 750 divided by 100 is 7.5; divided by 125 is 6; divided by 150 is 5. In hospitality, 125 or 150 millilitres is poured more often than 100, so for guests count on 6 glasses per bottle rather than 7.

European rules lay down which contents sizes pre-packed drink may have, and those lists differ per product type. Directive 2007/45/EC contains them, and the Netherlands has adopted that in the Warenwetbesluit hoeveelheden voorverpakkingen.

The permitted sizes are:

• non-sparkling wine: 100, 187, 250, 375, 500, 750, 1,000 and 1,500 ml
• sparkling wine: 125, 200, 375, 750 and 1,500 ml
• liqueur wine and aromatised wine: 100, 200, 375, 500, 750, 1,000 and 1,500 ml
• spirit drinks: 100, 200, 350, 500, 700, 1,000, 1,500, 1,750 and 2,000 ml
• yellow wine: 620 ml

The 700 millilitre size is not on the wine list, and 750 millilitres is not on the list for spirits. That is where the difference between the wine bottle and the spirits bottle comes from.

A 70 centilitre bottle yields 20 shots of 35 millilitres, the pouring measure the Trimbos-instituut uses for a standard glass of spirits at 35 percent.

If you pour more generously, it goes quickly: at 50 milliliters per glass, the same bottle yields 14 drinks. A bottle of 50 centiliters gives 14 drinks of 35 milliliters, a litre bottle 28. For a cocktail with 50 milliliters of base spirit, you can therefore count on 14 cocktails per bottle of 70 centiliters. The mandatory serving measure for genever was abolished in 1996, by the way; the measures you see now are habit, not law.

A standard glass contains about 10 grams of pure alcohol, about 12 millilitres, regardless of the type of drink. That is a unit of calculation, not a serving measure.

The Trimbos-instituut works with 250 millilitres of beer of 5 percent, 100 millilitres of wine of 12 percent and 35 millilitres of spirits of 35 percent. Alles over drinken, an initiative of Verslavingskunde Nederland together with the Ministry of Health, Welfare and Sport (VWS), converts that into whole bottles: a bottle of wine of 750 millilitres and 12 percent counts as 7 standard drinks, a bottle of port of 20 percent counts as 12, and a bottle of spirits of 35 percent counts as 21. A bottle of beer of 330 millilitres and 5 percent equals 1.3 standard drinks; a speciality beer of 8 percent in the same bottle equals 2.1.

A keg of beer of 50 litres gives 200 glasses of 250 millilitres, and a magnum of wine of 1.5 litres gives 15 glasses of 100 millilitres.

If you tap smaller flutes of 200 millilitres, 250 glasses come out of the same keg of 50 litres. With a magnum you get 12 glasses of 125 millilitres or 10 of 150 millilitres. For sparkling wine the same calculation applies: a bottle of 750 millilitres gives 7 glasses of 100 millilitres with a little left over. Larger bottles up to 1.5 litres are also permitted for sparkling wine.

Calculate with glasses, not bottles: number of guests times the number of glasses per guest times the pouring measure, divided by the bottle content.

An example. Twenty guests who each drink two glasses of wine of 125 millilitres come to 40 glasses, or 5 litres. Divided by 750 millilitres that is almost 7 bottles. Twenty guests who each drink three glasses of beer of 250 millilitres come to 15 litres, so a little more than a keg of 20 litres or a third of a keg of 50 litres. Observe the age limit when pouring: serving alcoholic drink to anyone under 18 is prohibited, and a drink is alcoholic as soon as at twenty degrees Celsius it consists of more than half a percent by volume of alcohol.