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Tool · Dispensing

How much is left in the keg?

Put an opened keg on the scales, subtract the empty weight, divide by the density. That is all there is to it – except that the empty weight varies by more than a factor of three depending on the keg type, and is therefore almost never right when you estimate it.

Input gross weight and keg type Accuracy see below No sign-up

Inputs

Keg with contents, exactly as it stands on the scales.

Default 1.008 kg/l for an average full-strength beer. Water is 1.000. Alcohol-free and strongly brewed beer is higher – your own brewery knows the value.

For polyurethane kegs, bolted-on protective rings or your own re-weighed empty weight.

Result

–Litres in the keg
–of the capacity

–

–0.3 l glasses
–0.4 l glasses
–0.5 l glasses

Number of glasses without dispensing losses. What stays behind in foam, in tapping and in the line differs with the system and the line length and cannot be given a serious flat figure here.

The calculation

Remaining volume in litres = (weighed total weight − empty weight) ÷ density. At 3 bar and a few litres of gas volume, the carbon dioxide in the headspace weighs well under twenty grams; against the accuracy of the scales it does not count and is not included here.

Where the error comes fromimportant

It is not the formula that is imprecise, it is the empty weight. The values stored here are catalogue figures for bare stainless steel kegs. In practice they scatter: polyurethane cladding, protective rings, remains of old lettering, a heavier spear after a repair. Two kilograms of deviation on a 50-litre keg are around two litres of beer.

If you need it precisely, weigh one empty keg from your own stock once and enter the difference above as a correction. After that the calculation is right for the whole fleet.

Stored empty weights

The same values as in the identification aid on the main page. They apply to kegs without plastic cladding.

Keg typeCapacityHeightEmpty weight

What the value does not tell you

  • Whether the beer is still goodAn opened keg loses no volume, it loses quality. How long it keeps depends on temperature, system hygiene and whether counter-pressure was applied throughout – not on the fill level.
  • How much really still goes into the glassesThe down tube does not end at the bottom. By design, a residue stays in the keg – how much depends on the distance from the base of the particular spear system.
  • Whether the keg is tightA loss of weight overnight can be a leak – or a set of scales standing on a sloping floor. Weigh twice, in the same place.
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