Strike Water Temperature Calculator (Mash Infusion)
Temperature to heat your strike water so the mash lands at the target — Palmer’s infusion equation from grain weight, grain temperature and mash thickness (or a total water volume), with mash-tun heat loss as a fixed allowance or worked out from the tun’s weight and material. In °C or °F, kg or lb, litres, quarts or gallons, with mash volume, first runnings, a mash-out infusion and how much hot or cold water fixes a miss.
How it works
Strike T = (0.41 ÷ ratio) × (target − grain T) + target + tun loss (ratio in L/kg; 0.41 is the grain’s heat capacity relative to water — use 0.2 with qt/lb); tun from weight: loss = tun kg × specific heat × (target − tun T) ÷ water L; infusion to raise the mash: water = (T₂ − T₁) × (0.41 × grain kg + mash water L) ÷ (infusion T − T₂)
Dry malt is cool and absorbs heat, so the water you pour in must be hotter than the mash you want. The Palmer infusion equation balances the heat: grain has about 0.4 times the specific heat of water, so at a typical 2.8 L/kg ratio each degree the grain must rise costs the water about 0.15 degrees. Thick mashes need hotter water than thin ones; brew-in-a-bag at 6 L/kg needs only two or three degrees above target. You can give the water as a ratio or as the total volume you plan to use, in litres, quarts or gallons, and every temperature in °C or °F. The tun’s own heat loss — cold plastic or steel soaking up warmth in the first minute — can be a fixed allowance you learn from your equipment (typically 1–3 °C), or worked out from the tun’s weight, its material’s specific heat and its starting temperature, the way brewing software does it. The same heat balance tells you how much boiling water a mash-out step needs and how much hot or cold water brings a missed mash back to target. Missing the mash temperature by a couple of degrees shifts fermentability noticeably, which is why this calculation matters.
Worked example
5.5 kg of grain at 20 °C, 2.8 L/kg, target 66 °C, 1.5 °C tun loss: 15.4 L of water at 0.146 × 46 + 66 + 1.5 = 74.2 °C (166 °F). In US units: 12.1 lb at 68 °F, 1.34 qt/lb, target 150.8 °F gives the same 165.6 °F. With a 2.5 kg plastic cooler at room temperature instead of the fixed allowance, the tun term is 2.5 × 0.30 × 46 ÷ 15.4 = 2.2 °C, so heat to 75.0 °C. If the mash then reads 64 °C, about 1.1 L of boiling water brings it back to 66 °C; a mash-out to 76 °C needs about 7.4 L of boiling water.
Sources: John Palmer, How to Brew — Calculations for boiling water additions · Brewer’s Friend — Strike water and mash heat loss
Frequently asked questions
What if I overshoot?
Add cold water or stir with the lid off for a minute. The correction table under the results gives the amount for your mash: with 5.5 kg of grain and 15.4 L, about 0.35 L of 15 °C water lowers it 1 °C.
Does this work for BIAB?
Yes — enter the full-volume ratio (often 5–7 L/kg) or the total water volume. The strike temperature will be only a few degrees above target, and if you heat the kettle with the grain in, choose “None” for the tun loss.
How do I enter °F, pounds and quarts?
Each field has its own unit menu: pick °F for the temperatures, lb for the grain and qt/lb for the ratio (or US gal for a total volume). The results show both °C and °F.
What number should I use for tun heat loss?
Start with about 1 °C (2 °F) for a pre-heated insulated cooler and 2–4 °C (4–7 °F) for a cold steel kettle, then adjust after each brew by how far you missed. Or choose the weight-and-material option: weigh the empty tun and the calculator works out its heat capacity.
Why does grain temperature matter so much?
The water has to warm the grain from its own temperature to the mash temperature. At 2.8 L/kg, every 5 °C colder grain needs about 0.7 °C hotter strike water — grain stored in a cold garage in winter can make you miss by 2 °C or more.
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This calculator is for educational purposes. Double-check important results before acting on them.