Cans, litres, and what actually fits

The conversion, roughly

A standard 330 ml can takes about 0.7 L of space once you allow for the gaps between cylinders. That is why 15 L is quoted as 18 cans, 22 L as 35 cans, 23 L as 33 cans and 28 L as 45 cans. Those figures are the bag packed tight with drinks and nothing else — which is almost never how a cooler leaves the house.

What the sizes look like in real life

15 L is a lunch for one with drinks, or an evening picnic for two. 22 L is a beach day for two with ice. 23 L on your back is a picnic for four with both hands free. 28 L is a cookout: a case of drinks, a bag of ice and the food. If you are between two, the honest test is not what fits in the bag but what you can carry from the car in one trip.

Ice takes a third of the bag

Plan on a quarter to a third of the volume being ice on a hot day. A 33-can pack realistically carries 24 cans and enough ice to keep them cold, and that is the right trade. Load a cooler to its can rating with no ice and you own a very well-made bag of warm drinks.

Shape matters as much as volume

A tall body keeps bottles upright and fits in a boot footwell; a wide body takes food containers flat and loads faster at a table. Backpacks want the tall shape, car coolers want the wide one. Both of ours fold flat, so the decision is about the day rather than the storage.