Strike Water & Mash Infusion Calculator
The water temperature to hit your mash-in target, and how much near-boiling water to add for a step infusion partway through, from John Palmer's two infusion equations.
1.25–1.5 qt/lb is typical.
How this was worked out
T_strike = (0.2 ÷ 1.25) × (152 − 70) + 152 = 165.12°F
Why strike water runs hot
Grain has thermal mass, and it usually starts well below your target mash temperature. When cool grain and hot water mix, the result settles somewhere between the two — so if you want the mash to land at, say, 152°F, the water has to start noticeably hotter than 152°F to pull the average up to it once the grain has cooled it back down.
Palmer's equation captures that with the ratio of water to grain: a thinner mash (more water per pound) has more hot water to do the work, so it needs a smaller overshoot. A thicker mash needs the water to run hotter to compensate for having less of it.
Worked example
10 lb of grain at 70°F, mashed at 1.25 qt/lb, targeting 152°F.
Strike water needs to be 165.12°F — about 13°F above the mash target, to absorb the grain's cooling effect.
Stepping the mash up mid-way
A single infusion mash can also be moved to a higher temperature partway through — common for a beta-amylase rest followed by an alpha-amylase step — by adding a measured amount of near-boiling water rather than applying direct heat. The second equation solves for how much: it depends on how far the temperature has to move, how much grain and water are already in the tun, and how hot the water being added is.
Worked example
10 lb of grain, 15 qt of water already in the mash, sitting at 122°F, stepping up to 154°F with 212°F water.
Adding 9.38 qt of boiling water gets the mash to the new target.
Common mistake
Using the grain-to-water ratio from your initial mash when working out a step infusion, instead of the water actually sitting in the tun at that point. The step infusion equation needs the current water volume, which is your original strike water plus anything added since — not the ratio you started with.
Keep going
- A gravity reading taken straight off warm mash or wort needs a temperature correction before it means anything, which is the next thing you'll want once the mash is running. Hydrometer correction Calculator
Frequently Asked Questions
Why is strike water hotter than the mash temperature I actually want?
Because the grain is colder than your target and has real thermal mass. Pouring water at exactly your target temperature onto room-temperature grain pulls the mix down below target every time. The equation overshoots the water temperature by just enough to land the combined mash where you want it.
What if I consistently miss my target temperature?
The 0.2 constant in the equation is an approximation for heat absorbed by the mash tun and grain together, and real equipment varies. If you consistently undershoot, raise the constant for your own system (effectively increasing R's numerator); if you overshoot, lower it. Most brewers land within a couple of degrees using 0.2 as-is.
Does grain temperature actually matter that much?
Yes, especially for a small batch. Grain pulled straight from a cold garage versus grain at room temperature can shift the strike water number by several degrees for the same target, because the temperature gap the water has to close is bigger.
Why does the step infusion formula use water already in the mash, not just grain weight?
Because you are heating everything in the tun, not just the grain — the existing mash water has its own thermal mass that dilutes the effect of the hot water you are adding. Leaving it out would overstate how much boiling water you need.
Can I use these equations in Celsius?
Yes, with one change: use 0.41 instead of 0.2 as the constant in both equations when your temperatures are in Celsius and your ratio is in litres per kg. Everything else in the equations stays the same.
Source and an honest caveat. Both equations are John Palmer's, from How To Brew, p.170. howtobrew.com itself could not be fetched — the site currently serves its book content through client-side JavaScript rather than static HTML, which blocks a plain fetch and an archived copy alike. Both equations, citing Palmer's book and page number, are reproduced verbatim by Diesel's Brewing Spreadsheet reference page, retrieved 22 September 2026. The strike water equation is independently corroborated — same form, same 0.2 constant — by Homebrew Academy's strike water calculator page, also retrieved 22 September 2026, whose own worked example (r=1.25 qt/lb, grain 70°F, target 152°F) matches this page's worked example exactly. This is a calculation tool; it does not account for equipment losses beyond the 0.2 constant.
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