Mash and sparge water calculator
Water accounting is where most all-grain brew days go wrong. Grain absorbs water and the boil evaporates it.
L per kg
minutes
% per hour
L per kg
Strike water
15.00L
- Sparge water
- 14.44
- Total water
- 29.44
- Pre-boil volume
- 24.44
- Absorbed by the grain
- 5.00
- Boiled off
- 2.44
- First runnings
- 10.00
- Overall water to grain ratio
- 5.889 L/kg
Show the working
- Grain bill = 5
- Mash thickness = 3
- Volume into the fermenter = 20
- Boil time = 60
- Evaporation rate = 10
- Grain absorption = 1
- Kettle and trub loss = 2
- Strike water = 5 * 3 = 15
- Absorbed by the grain = 5 * 1 = 5
- Pre-boil volume = (20 + 2) / (1 - 10/100 * 60/60) = 24.4444
- Total water = 24.4444 + 5 = 29.4444
- Sparge water = max(29.4444 - 15, 0) = 14.4444
- First runnings = max(15 - 5, 0) = 10
- Boiled off = 24.4444 - 20 - 2 = 2.444 44
- Overall water to grain ratio = 5 > 0 ? 29.4444 / 5 : 0 = 5.888 89
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- pre-boil volume = (batch + losses) / (1 - evaporation fraction)
- total water = pre-boil volume + grain absorption
Grain absorbs roughly one litre per kilogram, though a well-drained mash tun gives back a little more.
Evaporation depends on kettle geometry and how hard the boil is, not just on time. Measure yours once and reuse the figure.