Sparge Water Volume Calculator

About this calculator

In all-grain brewing, sparging is the step where hot water rinses residual sugars out of the mashed grain bed after the initial mash runoff, and getting the sparge volume right is what makes the difference between hitting your target pre-boil volume and either diluting the wort too much or leaving sugar behind in the grain. The calculation works backward from the target pre-boil kettle volume: sparge water needed = pre-boil volume − first-runnings volume (mash water minus what the grain bill absorbs, since grain typically retains roughly 0.5-0.6 liters of liquid per kilogram), plus an allowance for boil-off and equipment deadspace losses depending on the system.

Home and craft brewers use this calculation every time they build a recipe for a new grain bill or batch size, since pre-boil volume, mash water and grain absorption all shift with recipe changes, and a miscalculated sparge volume is one of the most common causes of an off-target original gravity on brew day. It applies to both batch sparging and fly sparging setups, though the target numbers plug into the same underlying volume math either way.

This calculator takes your target pre-boil volume, mash water volume and total grain weight, and returns the sparge water volume you need to add.