BrewGearCalc

Calculator

Mash and Sparge Water Calculator

Updated 2026-09-17 · BrewGearCalc

Quick answer

Strike, sparge and total water, with absorption and boil-off flagged as the conventions they are.

The arithmetic is standard. The two numbers that decide whether it is right for YOUR system are conventions: grain absorption near 0.125 gallons per pound, and your boil-off rate. Measure both once by recording your actual volumes on a brew day, and this calculator becomes accurate instead of approximate. A negative sparge volume is a real result, not an error: it means the mash already holds more water than the batch needs, which is how no-sparge brewing works.

Pounds
Quarts per pound
Gallons into the fermenter
Gallons per hour, measure your own
Minutes
Gallons per pound, convention
Gallons left behind
Strike water -
Sparge water -
Total water needed -
Pre-boil volume -
Absorbed by grain -
Lost to boil-off -

The formula

strike = grain_lb x ratio / 4pre-boil = batch + boil-off + kettle deadspacetotal = pre-boil + (grain_lb x absorption)sparge = total - strike

The arithmetic is standard. The two numbers that decide whether it is right for YOUR system are conventions: grain absorption near 0.125 gallons per pound, and your boil-off rate. Measure both once by recording your actual volumes on a brew day, and this calculator becomes accurate instead of approximate. A negative sparge volume is a real result, not an error: it means the mash already holds more water than the batch needs, which is how no-sparge brewing works.

What rests on a standard and what rests on convention

  • Standard The volume arithmetic itself.
  • Convention Grain absorption near 0.125 gal/lb and typical boil-off rates.

A standard is a published equation, a published constant or a manufacturer specification. A convention is widely repeated brewing practice with no governing document behind it. Both are useful. Confusing one for the other is how a habit ends up being quoted as a fact.

Mash tuns and kettles

This grid re-orders itself against the numbers you enter above. Prices are those returned when the page was built and change often.

Related on BrewGearCalc

Frequently asked questions

Why do I always finish short of my target volume?
Grain absorption is the usual culprit. At roughly an eighth of a gallon per pound, a twelve pound grain bill keeps about a gallon and a half in the spent grain, and it never reaches the kettle. Boil-off and kettle deadspace account for most of the rest. Brewers who ignore these consistently end up with a smaller, stronger batch than the recipe intended.
Can I mash with all the water and skip the sparge?
Yes. That is full volume or no-sparge brewing, and most all-in-one electric systems are run this way. It costs a few points of efficiency because the grain never gets rinsed, so the grain bill goes up slightly to compensate. In exchange the brew day loses a whole stage and a vessel.
How do I measure my own boil-off rate?
Mark a stick or use the kettle graduations. Note the volume at the start of the boil and again at the end, at the same temperature, and divide the difference by the boil length in hours. Boil-off depends on your burner, kettle diameter and how humid the air is, so a figure from someone else does not transfer.

Researched from published brewing formulas, manufacturer specifications and verified owner reviews. This is general guidance, not professional advice.