Brew water volumes

It is every beginner's number one question: how much water do I need? Much more than the volume of beer, because water is lost at every step. The grain holds back about a litre per kilo. The boil evaporates several litres. The sediment at the bottom of the kettle keeps a little more.

With too little water, you get less beer than planned, and stronger. With too much, the beer is thinner and the fermenter overflows. Calculating the volumes in advance lets you prepare the right amounts of mash and sparge water, and know where you stand during the brew.

The tool works back through the brew, from the fermenter to the mash tun:

cold volume   = fermenter + trub losses
hot volume    = cold volume / 0.96
pre-boil      = hot volume + boil-off × time
total water   = pre-boil + absorption × grain + tun losses
mash water    = ratio × grain
sparge water  = total water − mash water

The factor 0.96 accounts for expansion: boiling wort takes up 4% more than at 20 °C. The usual mash thickness is 2.5 to 3.5 L of water per kilo of grain. For no-sparge brewing, all the water goes into the mash: choose “Yes” for no-sparge brewing.

• The result depends on your boil-off rate and your losses: measure them on a first brew.
• The absorption of one litre per kilo applies to normally drained grain; a squeezed brew bag holds back less.
• The tool reports an error if the mash water exceeds the total water: lower the mash thickness.