Mash Strike Water Temperature Calculator

When you pour hot water onto cold grain, the temperature drops. How much it drops depends on how much water you are adding relative to the grain, and how cold the grain started. Getting this calculation wrong means starting your mash too hot (enzymes denature above 168°F) or too cold (conversion is sluggish below 146°F).

The formula comes from John Palmer’s book How to Brew and is the industry standard for homebrewers:

strike_temp = (0.2 / R) × (target_mash_temp - grain_temp) + target_mash_temp

Where R is the mash thickness in quarts of water per pound of grain.

The constant 0.2 gets described as “the specific heat of malt” all over the internet, and that is not quite what it is. Dry malt holds about 0.4 times as much heat per pound as water does. The other half of the constant is a unit conversion: R is quarts of water per pound of grain, and a quart of water weighs 2.086 lb, so the ratio has to be divided by 2.086 to compare like with like. 0.4 ÷ 2.086 = 0.192, which everyone rounds to 0.2.

That matters if you ever work in metric, where R is liters per kilogram and the same physics gives 0.41 instead. Same equation, different unit baggage.

Example: mashing at 154°F, with a 1.25 qt/lb ratio, grain at 65°F: strike_temp = (0.2 / 1.25) × (154 - 65) + 154 = 0.16 × 89 + 154 = 14.24 + 154 = 168.24°F

So heat the strike water to about 168°F before adding it to the grain. It will settle about 14°F lower once the grain goes in, landing on the 154°F you asked for.

Common mash thickness ratios:

• Thin mash (1.5 qt/lb): easier to stir, slightly better conversion efficiency, more dilute wort
• Medium mash (1.25 qt/lb): the most common for most styles
• Thick mash (1.0 qt/lb): better for body and mouthfeel, harder to stir, slightly lower efficiency

The malt temperature matters more than people expect. Grain stored in a cold garage in winter can be 50°F, and at 1.25 qt/lb that pushes the strike water about 2.4°F higher than the same recipe with 65°F grain. Thin mashes are more forgiving here, thick ones less: at 1.0 qt/lb the same 15-degree swing in grain temperature moves the strike target by 3°F.

Nothing in this formula knows about your mash tun. A cold cooler steals several degrees on its own, which is why preheating with a gallon of hot water and dumping it out before you strike is worth the two minutes. An uninsulated metal pot on a burner is a different problem again, since you can just apply heat and stir.

After the first few batches with a given setup, note whether your actual mash temperature runs slightly high or low versus the formula and adjust accordingly. Every system has its own thermal characteristics, and yours will be consistent once you know it.