Strike Water Calculator
Strike water temperature is the temperature at which mash water must be heated so that it settles to a target mash temperature after absorbing heat from dry grain. The calculation is strike temp = (0.3822 / R) × (target − grain temp) + target, where R is the water-to-grain ratio in liters per kilogram. A thinner mash needs a smaller overshoot.
Dry grain absorbs heat from the water. Strike water has to start hotter than the mash temperature you want, and how much hotter depends on the ratio.
Why strike water runs hot
Grain has a specific heat of roughly 0.38 relative to water, so when hot water hits dry grain the mixture settles somewhere between the two temperatures — much closer to the water, but not at it. To land on your mash temperature you have to start above it.
strike temp = (0.3822 / R) × (target − grain temp) + target
where R is the water-to-grain ratio in liters per kilogram. The thinner the mash, the less the grain pulls the temperature down, so the smaller the overshoot needs to be.
Strike temperature for a 3 L/kg mash with grain at 20 °C
| Target mash temp | Strike temp | Strike temp |
|---|---|---|
| 62 °C / 144 °F | 67.4 °C | 153.3 °F |
| 64 °C / 147 °F | 69.6 °C | 157.3 °F |
| 66 °C / 151 °F | 71.9 °C | 161.4 °F |
| 68 °C / 154 °F | 74.1 °C | 165.4 °F |
| 70 °C / 158 °F | 76.4 °C | 169.5 °F |
What the mash temperature does
The mash temperature decides how fermentable the wort is, because it decides which enzyme does most of the work.
- 62–64 °C — beta-amylase favored. Highly fermentable wort, drier beer, lower final gravity.
- 65–67 °C — the usual compromise. Balanced body, predictable attenuation.
- 68–70 °C — alpha-amylase favored. More unfermentable dextrin, fuller body, higher final gravity.
A two degree difference in mash temperature can move final gravity by three or four points, which is why the same recipe brewed twice can finish in different places.
Things this calculation does not know
It assumes the tun itself is at the same temperature as the grain. A cold steel or plastic mash tun will absorb heat too, typically costing one to two degrees on the first mash of the day. Preheat the tun with hot water, or add a degree or two to the strike temperature and expect to correct.
Grain absorbs roughly 1 liter per kilogram and keeps it, which is why the volume that comes out of the tun is always less than the volume that went in.
Strike Water Calculator — questions
What water-to-grain ratio should I use?
Around 2.6–3.2 L/kg (1.25–1.5 quarts per pound) for a traditional mash. Brew-in-a-bag brewers often mash much thinner, at 4 L/kg or more, which needs a lower strike temperature because there is proportionally less grain to heat.
My mash came in low. What now?
Add boiling water and stir, or apply direct heat if your tun allows it. Roughly 1 liter of boiling water per 20 liters of mash raises the temperature by about 2 °C. Overshooting is harder to fix, so approach from below.
Does grain temperature really matter?
Yes, more than people expect. Grain stored in a cold garage at 5 °C rather than a 20 °C kitchen needs several degrees more on the strike water for the same target.
Strike temperature from the recipe, not a second tab
Brewgravity calculates strike water from your grain bill and equipment profile automatically — one less page to type numbers into on brew day.
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