Brewing Water & Sparge Volume Calculator
Mash, sparge and total water from grain weight, boil-off, absorption and losses.
How it works
Brew-day water accounting works backwards from the volume you want in the fermenter. Mash water is grain times the mash ratio; the grain absorbs about 0.96 L/kg; boil-off is the evaporation rate over the boil. Pre-boil volume is your batch plus losses plus boil-off, and total water also covers absorption. Sparge water is the total minus the mash.
mash = grain × ratio
absorption = grain × 0.96
boil-off = rate × hours
pre-boil = batch + losses + boil-off
total = pre-boil + absorption
sparge = total − mash
Sources: brew-day water accounting from Brewer's Friend.
Estimates for planning - boil-off, absorption and deadspace vary by system, so calibrate against your own measured volumes.
Frequently asked questions
- How much water do I need for an all-grain batch?
- You need enough for your fermenter volume plus everything lost along the way: grain absorption (~0.96 L/kg), boil-off, and trub/kettle loss. This calculator adds those up and splits the total into mash and sparge water.
- How much water does grain absorb?
- Roughly 0.96 L per kg of grain (about 0.12 gal/lb). Heavier grain bills lock away more water, so total water and sparge volume rise with grain weight.
- What is pre-boil volume?
- Pre-boil volume is the wort in the kettle before the boil starts: your target batch into the fermenter, plus trub/kettle loss, plus the water that will boil off. Boil-off is the rate times the boil length.