Mash Water Volume Calculator
Calculate mash water and sparge water volumes for all-grain homebrewing.
Based on grain weight, water-to-grain ratio, and target pre-boil volume.
Mash water volume is the amount of hot water mixed with crushed grain in the mash tun to convert starches to fermentable sugars. Getting the volume right ensures proper enzyme activity, efficiency, and a manageable mash consistency.
The Formula:
Strike water volume (liters) = Grain weight (kg) × Water-to-grain ratio (L/kg)
Water-to-Grain Ratio Guidelines:
| Ratio | Mash Thickness | Notes |
|---|---|---|
| 2.0 L/kg | Very thick | High efficiency, harder to stir |
| 2.6 L/kg | Thick | Traditional British style |
| 3.0 L/kg | Medium | Most common for homebrewers |
| 3.9 L/kg | Thin | Easy to stir, slightly lower efficiency |
| 4.7 L/kg | Very thin | Single infusion, simple mashes |
Strike Temperature Formula:
Strike temp (°C) = [(0.41 / R) × (T_mash − T_grain)] + T_mash
Where:
- R = water-to-grain ratio
- T_mash = target mash temperature (typically 65–68 °C)
- T_grain = grain temperature before mashing (typically 18–22 °C room temp)
Worked Example:
Grain bill: 5 kg, ratio: 3.0 L/kg, target mash temp: 67 °C, grain temp: 20 °C.
Strike water volume = 5 × 3.0 = 15 liters
Strike temp = [(0.41 / 3.0) × (67 − 20)] + 67 = [0.137 × 47] + 67 = 6.4 + 67 = 73.4 °C
Heat your water to 73–74 °C; adding the grain will drop it to the 67 °C target.
Sparge Water:
Sparge water = (Pre-boil volume + Grain absorption) − Strike water volume
Grain absorbs approximately 0.8–1.0 L per kg of grain.
Grain absorption = 5 kg × 0.9 = 4.5 L → Sparge water = (25 L pre-boil + 4.5 L) − 15 L = 14.5 liters
Practical Tips:
- Preheat the mash tun with hot water before striking — cold equipment steals heat from your mash
- Stir thoroughly when adding grain to avoid dough balls (dry clumps of grain)
- Check mash temperature 10 minutes in and adjust with hot or cold water if needed
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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