Mash Water Calculator

Understanding Mash Water Calculations

All-grain brewing requires careful water management to hit your target mash temperature and collect enough wort for your boil. The key calculations involve strike water temperature, mash water volume, and sparge water volume.

Strike Water Temperature

When you add hot water to room-temperature grain, the water temperature drops. The strike water formula calculates how hot your water needs to be to reach your target mash temperature after the thermal exchange with the grain:

Strike Temp = (0.2 / R) × (T_mash - T_grain) + T_mash

Where R is your water-to-grain ratio in qt/lb, and 0.2 is the specific heat of grain (relative to water). This is the industry-standard formula used by virtually all brewing software.

Mash Thickness

The water-to-grain ratio affects enzyme activity, lautering efficiency, and temperature stability:

• Thin mash (1.5-2.0 qt/lb): Better enzyme mobility, easier to stir, more temperature-stable. Good for beginners and batch sparging.
• Thick mash (1.0-1.25 qt/lb): Concentrates enzymes for potentially higher efficiency. Common in traditional British brewing. Requires more sparge water.
• BIAB (2.5-4.0+ qt/lb): Brew-in-a-bag uses all water in the mash with no sparge. Very thin ratio.

Grain Absorption

Grain absorbs about 0.125 gallons (0.5 quarts, or 0.52 L/kg) of water per pound. This water is lost in the spent grain and never makes it to your kettle. Knowing this helps you calculate sparge water requirements.

Sparge Water

Sparge water rinses additional sugars from the grain bed after the mash. The volume needed is:

Sparge Volume = Target Pre-Boil Volume - (Strike Volume - Grain Absorption)

Temperature Tips

• Preheat your mash tun with hot water to reduce heat loss
• Add 2-5°F to your strike temperature to account for equipment heat loss (not included in this calculator)
• Stir the mash well after doughing-in and check temperature in multiple spots
• Sparge water should be around 168-170°F to stop enzyme activity and improve flow