💧 Mash Water Calculator
Calculate mash and sparge water volumes for your brew
Use this calculator to determine how much water you need for mashing and sparging. Essential for planning your brew day and hitting your target volumes and efficiency.
Total weight of all grains in recipe
Typical range: 1.25-1.5 qt/lb (3-3.5 L/kg)
Final volume into fermenter
Typical: 60 or 90 minutes
Evaporation rate (depends on your system)
Volume lost to kettle trub and equipment
📚 How It Works
This calculator works backward from your target batch size, accounting for all water losses throughout the brewing process:
Calculation Steps:
- Post-Boil Volume: Batch size + trub loss
- Boil-Off: (Boil time ÷ 60) × boil-off rate
- Pre-Boil Volume: Post-boil + boil-off
- Grain Absorption: Grain weight × 0.125 gal/lb (1.04 L/kg)
- Mash Water: Grain weight × mash thickness
- Sparge Water: Pre-boil + absorption - mash water
Mash Thickness Guide:
- 1.0-1.25 qt/lb (2.5-3.0 L/kg): Thick mash - better enzyme activity
- 1.25-1.5 qt/lb (3.0-3.5 L/kg): Standard - most common range
- 1.5-2.0 qt/lb (3.5-4.5 L/kg): Thin mash - easier stirring, BIAB
- 2.0+ qt/lb (4.5+ L/kg): Very thin - full volume BIAB/no sparge
Grain Absorption:
Grain absorbs approximately 0.125 gallons per pound (1.04 L/kg) of water. This is the volume of water that stays with the spent grain after lautering. Actual absorption can vary slightly based on grain crush and mash thickness.
System-Specific Adjustments:
- BIAB (Brew in a Bag): Use full volume, no sparge (2.5-3.0 qt/lb)
- Fly Sparging: Continuous sparge over 60-90 minutes
- Batch Sparging: 1-2 sparge additions, easier for beginners
- No Sparge: All water in mash (3.0+ qt/lb), lower efficiency
Common Issues:
- Missing volume target: Track your actual boil-off rate and dead space
- Stuck sparge: Check grain crush and don't compact grain bed
- Low efficiency: May need to adjust pH, crush, or sparge technique
- Too much volume: Extended boil or plan for dilution