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 (quarts) = Grain weight (lb) × Water-to-grain ratio (qt/lb)
The inputs on this page are pounds, quarts per pound, and gallons. If you brew in metric, the same equation is liters = kilograms × L/kg, and 1 qt/lb converts to 2.086 L/kg. Both forms appear in the table below so you can work in whichever your recipe uses.
Water-to-Grain Ratio Guidelines:
| qt/lb | L/kg | Mash Thickness | Notes |
|---|---|---|---|
| 0.96 | 2.0 | Very thick | High efficiency, harder to stir |
| 1.25 | 2.6 | Thick | Traditional British style |
| 1.44 | 3.0 | Medium | Most common for homebrewers |
| 1.87 | 3.9 | Thin | Easy to stir, slightly lower efficiency |
| 2.25 | 4.7 | Very thin | Single infusion, simple mashes |
Strike Temperature Formula:
Strike temp (°F) = [(0.20 / R) × (T_mash − T_grain)] + T_mash, with R in qt/lb
Strike temp (°C) = [(0.41 / R) × (T_mash − T_grain)] + T_mash, with R in L/kg
Where:
- R = water-to-grain ratio, in the units matching the constant
- T_mash = target mash temperature (typically 148–158 °F, 65–70 °C)
- T_grain = grain temperature before mashing (typically 64–72 °F, 18–22 °C room temp)
The two constants are the same physics. 0.20 × 2.086 = 0.417, and the metric convention rounds it to 0.41.
Worked Example:
Grain bill: 11 lb (5 kg), ratio: 1.44 qt/lb (3.0 L/kg), target mash temp: 152 °F (67 °C), grain temp: 68 °F (20 °C).
Strike water = 11 × 1.44 = 15.8 quarts, or 3.96 gallons (5 kg × 3.0 = 15 liters)
Strike temp = [(0.20 ÷ 1.44) × (152 − 68)] + 152 = [0.139 × 84] + 152 = 11.7 + 152 = 163.7 °F (73.1 °C)
Heat your water to about 164 °F; adding the grain will drop it to the 152 °F target.
Sparge Water:
Sparge water = (Pre-boil volume + Grain absorption) − Strike water volume
Grain absorbs roughly 0.125 gallons per pound, which is exactly half a quart per pound, or 1.04 L per kg. Published figures scatter between 0.8 and 1.2 L/kg depending on crush and how hard you squeeze a bag, so treat it as a starting point and adjust once you have measured your own system twice.
Grain absorption = 11 lb × 0.125 = 1.38 gal → Sparge water = (6.5 gal pre-boil + 1.38) − 3.96 = 3.92 gallons
Practical Tips:
- Preheat the mash tun with hot water before striking. Cold equipment steals heat from your mash and no formula accounts for it.
- 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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