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Sparge Water Calculator: Balance Your Brew-Day Volumes
Sparge water is the extra water needed to reach your pre-boil collection target after accounting for mash water and collection losses. Start with a target you can measure, then balance the volumes.
BrewMyBeer Editorial Team · Sources checked 24 September 2026 · Calculated examples, not laboratory measurements. How we create content
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The calculation
Sparge water = target pre-boil volume − mash water + grain weight × absorption rate + other unrecoverable mash loss.
All volume inputs use litres. Grain uses kilograms, and absorption uses litres per kilogram. Count each loss once. If your absorption measurement already includes a loss, do not add that loss again in the separate field.
An example you can check
Imagine a 25 L pre-boil target, 16 L of mash water, 4 kg of grain, an assumed absorption rate of 0.75 L/kg and 1 L of separate unrecoverable mash loss. The calculation is 25 − 16 + (4 × 0.75) + 1 = 13 L of sparge water.
Check the balance: 16 L mash + 13 L sparge = 29 L total water. Subtract 3 L retained by grain and 1 L of other loss; 25 L reaches the kettle. These are hypothetical inputs, so replace them with measurements from your equipment.
Where does the pre-boil target come from?
Work backward from the volume you want in the fermenter, accounting for kettle and transfer losses and expected boil-off. Keep the temperature basis consistent when comparing water and wort measurements. You can plan the first part with the mash-water calculator.
What if the answer is negative?
Your chosen mash water exceeds what this water balance needs. The tool asks you to review the inputs instead of suggesting a negative rinse. A no-sparge process needs its own water plan; do not remove wort simply to satisfy this calculation.
Method
Grainfather documents the underlying single-infusion water balance. The separate loss input makes an additional unrecoverable collection loss explicit. This is a volume planner; it does not set a sparging temperature, pH limit or efficiency target.
Before you use the result
- Count each loss once: absorption and other mash loss are separate inputs.
- Measure absorption and vessel loss on your own system.
- Keep the temperature basis consistent across volume readings.
A quick learning check
Your next brew loses 0.5 L more. What changes?
Try a craft decision game →Sources & further reading
These references explain the methods and limitations. The worked examples and learning questions on this page are BrewMyBeer calculations, not claims of hands-on testing.