Sparge Water Volume Calculator

How it is calculated

The tool works back from the pre-boil volume you want. absorbed = grain weight × 0.125, first runnings = mash water − absorbed and sparge water = pre-boil volume − first runnings. The constant 0.125 is gallons of water retained per pound of grain, so the calculation is in US gallons and pounds, the form is labelled gal and lb, and the answer is printed in gal. The target is the volume in the kettle before the boil, so there is no allowance for boil-off, trub or equipment dead space. Two situations show no result: the grain would absorb more water than you mashed with (no first runnings at all), or the first runnings already exceed the pre-boil target, which would make the sparge negative.

Common mistakes

• Entering litres and kilograms. The 0.125 constant is gallons per pound, so use US gallons and pounds, or convert a litre-and-kilogram recipe first.
• Entering the full boil volume (with boil-off) as the target. The target here is the pre-boil volume, which is what you need in the kettle before the boil starts.
• Forgetting that grain absorbs water. Using mash water as the first runnings volume would overstate it and leave you short of the target pre-boil volume.
• Entering mash water that is more than the pre-boil target allows (for example 9 gal of mash water for a 7 gal pre-boil with 11 lb of grain), or a tiny mash volume with a huge grain bill. Both show no result.
• Counting the sparge water temperature or equipment loss as part of the volume. The tool deals only with water volume and has no allowance for dead space.