How do you calculate strike water temperature?
Grain is cooler than the mash you want and soaks up heat as it wets, so the water has to go in hotter than the target — how much hotter depends on how much water carries the heat. Palmer's infusion equation is the one every calculator uses:
Tstrike = (0.2 ÷ R) × (Tmash − Tgrain) + Tmash
R is the water-to-grain ratio in qt/lb; in L/kg the constant becomes 0.41 (it's the same 0.2, converted — the equation doesn't care which units you brew in, and neither does this page).
Palmer's own example: grain at 70°F, target 152°F, 1.25 qt/lb → (0.2 ÷ 1.25) × 82 + 152 = 165°F. The metric mirror — 5 kg at 20°C, 3.0 L/kg, target 66°C — wants 72.4°C. The 0.2 is the heat capacity of malt relative to water: a pound of grain warms about as easily as a fifth of a quart of water, which is why the correction shrinks as the mash gets thinner. Add whatever your tun steals (below), heat the water, stir it in, wait five minutes, and read the mash.
Strike water temperature chart
For a preheated tun and grain at room temperature (68°F / 20°C). Read down your target, across your thickness; add your tun's loss on top.
| Target mash | Water : grain (qt/lb · L/kg) | ||||
|---|---|---|---|---|---|
| 1.00 · 2.1 | 1.25 · 2.6 | 1.50 · 3.1 | 1.75 · 3.7 | 2.00 · 4.2 | |
| 146°F · 63.3°C | 162°F · 72.0°C | 158°F · 70.3°C | 156°F · 69.1°C | 155°F · 68.3°C | 154°F · 67.7°C |
| 148°F · 64.4°C | 164°F · 73.3°C | 161°F · 71.6°C | 159°F · 70.4°C | 157°F · 69.5°C | 156°F · 68.9°C |
| 150°F · 65.6°C | 166°F · 74.7°C | 163°F · 72.8°C | 161°F · 71.6°C | 159°F · 70.8°C | 158°F · 70.1°C |
| 152°F · 66.7°C | 169°F · 76.0°C | 165°F · 74.1°C | 163°F · 72.9°C | 162°F · 72.0°C | 160°F · 71.3°C |
| 154°F · 67.8°C | 171°F · 77.3°C | 168°F · 75.4°C | 165°F · 74.1°C | 164°F · 73.2°C | 163°F · 72.6°C |
| 156°F · 68.9°C | 174°F · 78.7°C | 170°F · 76.7°C | 168°F · 75.4°C | 166°F · 74.5°C | 165°F · 73.8°C |
| 158°F · 70.0°C | 176°F · 80.0°C | 172°F · 78.0°C | 170°F · 76.7°C | 168°F · 75.7°C | 167°F · 75.0°C |
Palmer's infusion equation, from this page's engine. Colder grain: add about 1°F for every 4°F it is below 68 (0.25°C per °C) at 1.5 qt/lb. Cold cooler: add your measured tun loss, typically 2–5°F / 1–3°C.
Why did I miss my mash temperature?
The equation is exact for grain and water. Everything else on your brew day is a small error it can't see, and they add up. Around a 152°F mash at 1.5 qt/lb:
| What changed | Strike water needs to be |
|---|---|
| Grain 10°F / 5.5°C colder (from the garage) | +1.3°F / 0.7°C |
| Thicker mash, 1.25 qt/lb (2.6 L/kg) | +2.2°F / 1.2°C |
| Thinner mash, 2.0 qt/lb (4.2 L/kg) | −2.8°F / 1.6°C |
| Full-volume BIAB, ~3 qt/lb (6 L/kg) | −5.4°F / 3.0°C |
| Cold plastic cooler, not preheated (typical) | +4.0°F / 2.2°C |
First four rows from the equation; the cooler row is a typical measured value, not a formula — which is the point of the next section.
A cold plastic cooler or steel tun soaks up a surprising amount of heat in the first minute; a preheated one, an insulated kettle or an all-in-one system takes almost none. Brew with the equation's number, stir, wait five minutes, read the mash. If it's 3°F low, your tun's loss is 3°F — type it in the box above, save it, and the next brew lands. That single number replaces every "add a few degrees to be safe" you've read. (Or preheat: a kettle of hot water swirled in and dumped a few minutes before strike takes the tun to zero.)
What if the mash comes in high or low?
The same equation, run for an addition instead of the first infusion, tells you what to add. A 5 kg mash in 15 L sitting 3°C hot comes down with about 1.0 L of tap water at 15°C; the same mash 3°C cold comes up with 1.5 L of boiling water. The calculator's "if the mash lands off target" rows do this for your numbers. Two rules: fix hot mashes fast — the first ten minutes at 158°F when you wanted 150 have already made the wort less fermentable — and don't panic over 1°F. Your thermometer isn't that good, and neither is the difference in the beer.
At full-volume BIAB thickness (around 6 L/kg or 3 qt/lb) the strike water only needs to be about 3.2°C above the target — versus 6.4°C at 3 L/kg — because there's so much water carrying heat that the grain barely dents it. And a mash that thin holds its temperature the same way, which is why BIAB brewers rarely think about this page and cooler brewers think about it a lot. Grain at 15°C versus 25°C moves the answer by 1.4°C at 3 L/kg; measure the grain, not the room.