Mash + Sparge Water Calculator
How to use the Tool
Everything you enter lives above the results. Update once, then scroll down and brew from the plan.
Inputs and settings
Pick your method first, then units. The tool hides irrelevant fields to keep you moving.
BIAB and no-sparge set sparge water to zero and focus on total water and losses.
Your target after cooling and transfer losses. This is the number you actually care about.
Boil length drives evaporation. Do not let the tool guess.
Lower tends to ferment drier, higher tends to finish fuller. Most live around 64 to 68°C.
Cold grain steals heat, winter brewing is where this input earns its keep.
The anchor number. Absorption and mash volume scale from this.
Set your mash thickness. If your mash tun is tight, this is where you prevent overflow.
Measure once, then reuse. Rolling boil evaporates more than a timid simmer.
What stays behind in kettle, hoses, chiller, and sludge.
Hot wort contracts as it cools. Keeps hot volumes honest.
Crush and grain type change this. Start with default, then calibrate.
Liquid you cannot drain due to false bottom, manifold, or outlet height.
Pick how you measure on brew day, then use the tip under the dropdown.
Tip: Many kettle markings are off. Calibrate once with measured water, then trust your numbers.
Shown only for batch or fly sparge modes.
1 is common. 2 can help distribution and prevent overfilling.
Optional. Slower runoff helps reduce channeling.
Advanced system tuning (use after you measure your setup)
Set to 0 to ignore. If set, the tool warns you before overflow.
Used for mash volume estimates. Defaults are fine for most brewers.
Preheating makes strike temp predictions more reliable.
If you consistently mash low, add a small bump, then refine later.
If your thermometer reads high by 0.5°C, enter +0.5. The tool compensates your target readings.
Shows stuck sparge prevention tips. It does not change the math.
Squeezing reduces effective absorption. Only used in BIAB mode.
Used for the optional timeline in the brew day view.
Used for the timeline view.
A quick guardrail. Avoid common mistakes without a full water chemistry tool.
Assumptions and definitions (for trust)
Outputs and brew day plan
Heat strike water
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--
Target pre-boil volume
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--
Sparge water
--
--
End-of-boil hot volume
--
--
Where the water went
- Total water needed: --
- Grain absorption: --
- Mash tun dead space: --
- Boil-off (total): --
- Trub and transfer loss: --
- Shrinkage applied: --
If this looks wrong, your system-loss inputs need calibration, not your recipe.
Capacity and checks
- Estimated mash volume: --
- Mash tun capacity: --
- First runnings: --
- Recommended sparge water temp: --
Volume sanity: label readings as hot in kettle vs cooled in fermenter.
If reality does not match the plan, pick what went wrong and follow the playbook.
The brew day view for your phone.
Tap Update results to generate your brew day checklist.
Rescue playbook
- Pick your method first. Batch sparge and fly sparge split water into mash water and sparge water. BIAB and no-sparge focus on total water up front.
- Choose units and stick with them. Metric or imperial, pick one for the session so your notes match your measurements.
- Set your target into the fermenter. This is post-chill and post-transfer. Everything else is the tool protecting that number.
- Enter boil time and boil-off rate. Boil-off is system-specific. If you have never measured it, do a water-only 60 minute boil and record the drop.
- Enter grain weight, mash ratio, and temperatures. Grain weight drives absorption. Grain temperature prevents winter mash disappointment. Ratio prevents mash tun overflow.
- Dial in losses honestly. Dead space and trub loss are not mistakes, they are plumbing and physics. Get them right once and reuse forever.
- Pick your volume measurement method. Kettle marks lie more often than brewers admit. Dipsticks and weighing are boring and accurate.
- If sparging, set only what matters. Batch sparge additions (usually 1 or 2). Fly sparge runoff time (optional, but useful for slowing down).
- Tap Update results and brew from the outputs. The four result cards are your compass, the checklist is your hands-on steps.
- If results look wrong, calibrate. Compare predicted versus actual pre-boil, end-of-boil hot volume, and into-fermenter volume. Adjust boil-off and trub first, then absorption and dead space.
Mash and sparge decisions that actually matter
The point of mash and sparge planning is to control two things that decide whether brew day feels calm or chaotic: volume and extraction.
Volume is logistics, can you land the right amount of wort in the kettle, then deliver the right amount into the fermenter. Extraction is the efficiency and flavour side, can you rinse sugars without dragging harshness with them.
This tool starts with volume because volume is what breaks first, then it supports extraction by preventing over-sparging, under-collecting, or chasing the wrong target at the wrong temperature.
If your pre-boil volume is low, you have two safe levers: add water or adjust the boil. Adding water is the fastest rescue and it keeps your hop schedule predictable, but it lowers gravity. Extending the boil concentrates the wort, which pulls gravity back up, but it can increase bitterness and deepen colour, and it costs time.
The experienced call is choosing what you value in that batch. If this is a hop-forward beer where balance matters, top up and accept a slightly lower ABV. If you are chasing a specific OG for a style or competition target, boil longer and accept the trade-off.
If your pre-boil volume is high, do not panic and do not suddenly turn the boil into a violent torch. High volume is usually measurement mismatch or over-estimated losses. First confirm you are reading hot kettle volume correctly and not confusing it with cooled volume.
Then decide: boil longer to hit end-of-boil volume, or keep the planned boil time and accept a lower OG. If this happens often, your boil-off rate or trub loss input is the culprit. Fix that input and the tool becomes brutally accurate.
Mash temperature issues are sneaky because they change fermentability. Mash low and you can finish thinner and drier. Mash high and you can finish fuller with a higher FG. The rescue approach is boring and effective: stir first, then re-check, stratification lies.
If you are low, add small amounts of boiling water, stir, and re-check, or apply gentle heat while stirring if your setup allows. If you are high, a small cool water addition can bring you down, or you can ride it out and accept a touch more body.
What matters most is stability.
Wild swings do more harm than being half a degree off.
Sparge problems are mostly about flow, temperature, and restraint. Runoff that slows or sticks is commonly a fine crush, a gummy grist (wheat, oats, rye), or a valve opened too far that compacts the bed. The fix is patience and gentle recirculation, then a slow restart.
Sparge water temperature should be sensible, and the real discipline is stopping when you hit your pre-boil volume target.
Chasing the last sugar drop can drag harshness and astringency into your kettle. Your palate will notice that long after you forget the tiny efficiency gain.