A Free Calculator · All-Grain Brewing · Updated 2026
What temperature should your strike water be?
Cold grain chills your mash water. To hit your target rest temperature, you need to
add the water hotter than that target — by an amount that depends on how much grain
you have, how cold it is, and how much water you are using relative to grain weight.
Enter those four numbers below and the calculator gives you the correct strike water
temperature plus your total water volume. Every formula is shown.
Strike water temp (°F)·Total water volume (qt & gal)·Palmer infusion formula
Read this first
This calculator uses the Palmer single-infusion strike water formula with a grain-to-water
specific-heat ratio of 0.2 — an empirical approximation from homebrew literature that works
well for most base-malt grain bills on an insulated cooler mash tun. It does not account
for your vessel's thermal mass; pre-heat your mash tun before doughing in for best results.
Inputs are in imperial units (pounds, quarts, °F). It is not intended for decoction or
recirculating (HERMS/RIMS) step mash systems.
Adjust any field and the result updates immediately. Defaults model a typical 10 lb grain bill mashed at 152°F with 1.25 qt/lb water.
Your grain bill
lb
Total weight of all grains in the mash — base malt plus any specialty malts.
°F
Temperature of the grain before mashing in — typically room temperature. Grain stored in a cold garage or basement will be cooler.
Target mash & water volume
°F
Your intended rest temperature. 148–152°F favors fermentability (drier beer); 154–158°F favors body (fuller beer). See the reference table below.
qt / lb
Quarts of strike water per pound of grain. Common range is 1.0–1.5 qt/lb; 1.25 is a widely used default. Thinner mashes need less-hot strike water.
Heat strike water to
Strike water temperature
Total strike water
Total strike water (gallons)
Temp overshoot above mash target
The formulas, in full
This is the Palmer single-infusion strike water equation — the same arithmetic you
could do on paper. The only judgment call is whether the 0.2 specific-heat constant
is close enough for your system; most brewers find it is.
How each number is derived
1 — Strike water temperature (the Palmer infusion formula)
strikeTemp (°F) = (GRAIN_WATER_THERMAL_RATIO / R) × (T2 − T1) + T2
where:
GRAIN_WATER_THERMAL_RATIO = 0.2 (empirical grain:water specific-heat ratio)
R = mash thickness (qt water per lb grain)
T1 = grain / room temperature (°F)
T2 = target mash rest temperature (°F)
Thickness and rest temperature interact. The table below shows typical mash thickness
ranges, the approximate rest temperatures associated with each body target, and how
they affect the finished beer. All values are approximate and vary by grain bill,
yeast strain, and fermentation temperature.
Thickness (qt/lb)
Typical rest temp range
Body & fermentability
Common use cases
1.0 – 1.1
150–156°F (approx.)
Thick mash — enzyme-concentrated, tends toward fuller body and slightly lower attenuation. Alpha-amylase favored at higher temps.
Stouts, porters, Scottish ales; styles where residual sweetness is desirable.
1.2 – 1.35
148–154°F (approx.)
Medium mash — balances fermentability and body. 152°F is the classic compromise between beta- and alpha-amylase activity.
American ales, IPAs, pale ales; most base recipes as a starting point.
1.4 – 1.5
146–152°F (approx.)
Thin mash — better enzyme mobility, improved fermentability, drier finish. More wort dilution; smaller total volume into kettle per pound of grain.
Dry lagers, session ales, highly attenuated styles; also used when sparge volume is limited.
1.6 – 2.0
145–150°F (approx.)
Very thin mash — high fermentability, low body. Less common; used in some lager or single-infusion decoction-mimic profiles.
Bohemian pilsners, dry German lagers; brewers chasing maximum attenuation.
Temperature ranges and body descriptions are approximate. Actual attenuation depends
heavily on yeast strain, pitch rate, fermentation temperature, and the specific grain bill.
Use these ranges as a starting point and adjust based on your own tasting results.
Why getting strike temperature right matters
The mash rest temperature determines which enzymes convert starch to sugar — and that
determines whether your beer is dry and fermentable or full-bodied and sweet. A
miscalculated strike temperature starts a chain reaction you cannot fully reverse
once the mash is underway.
Enzyme activity peaks in a narrow temperature window
Beta-amylase — the enzyme that produces highly fermentable maltose — denatures rapidly above roughly 158°F (70°C). Once it is gone, no amount of waiting brings it back. If your strike water is too hot and the mash climbs above your target, beta-amylase activity drops permanently for that batch. The result is less fermentable wort, a higher final gravity, and a sweeter, fuller-bodied beer than you designed. Alpha-amylase is more heat-stable and keeps working at higher temperatures, but it produces a broader mix of sugars including unfermentable dextrins. Knowing where your mash landed — not where you aimed — is the only way to predict the outcome reliably.
Grain temperature is the variable most brewers underestimate
The single biggest cause of missing a mash temperature is entering 70°F as a grain temperature when the grain is actually colder — stored in a basement at 60°F or a cold garage at 50°F. Every 10°F your grain is colder than assumed drops your mash temperature by roughly 1–2°F after doughing in. Measure grain temperature with a thermometer before mashing in, not from memory of room temperature. Similarly, grain that has been sitting in a warm brew space (75°F) will require less hot strike water than the default assumes.
Vessel heat absorption is a real but fixable variable
A cooler mash tun at room temperature will absorb heat from the mash water, dropping rest temperature below what the formula predicts. Pre-heating the vessel — filling it with hot water, closing the lid for a few minutes, and discarding the water before mashing in — eliminates most of this correction. If you skip this step, adding 1–2°F to the calculated strike temperature compensates. A stainless pot on a burner does not have this problem (you can apply direct heat), but an uninsulated pot in a cool garage loses heat the opposite direction during the rest itself.
How to get the most accurate result from this calculator
Four inputs drive the calculation. Three of them you set at brew time; the fourth
(the 0.2 constant) you can tune over several batches to account for your specific system.
Measure grain temperature — do not assume room temperature
The grain temperature input (T1) has a large effect on the result. Stick a thermometer probe into your grain bag or malt bucket the morning of brew day. Grain stored in an air-conditioned basement or a cool garage can be 10–15°F below what you might guess. A 10°F error in T1 translates to roughly a 1–1.5°F error in your mash temperature after doughing in.
Pre-heat your mash tun before doughing in
Fill the mash tun with hot water (it does not need to be at strike temperature — any warm water helps), close the lid, wait two or three minutes, then discard and immediately dough in. This brings the vessel to near the mash rest temperature and removes the vessel's thermal mass as a correction variable entirely. Skip this step and the vessel may absorb 1–3°F of heat from the mash water.
Track your actual rest temperature over a few batches
Measure mash temperature ten minutes after doughing in (after thorough stirring) and record the difference from the calculator's target. A consistent 2°F undershoot, for example, tells you to add 2°F to the strike water for your system. You can approximate this by entering a slightly lower grain temperature — two degrees colder is the practical equivalent of heating two degrees higher.
Use 1.25 qt/lb as a default mash thickness and adjust from there
Mash thickness affects strike temperature: a thinner mash (more water per pound) requires less overshoot above your target. If you are targeting a drier, highly fermentable beer, consider a thinner mash at 1.4–1.5 qt/lb combined with a lower rest temperature (148–150°F). If you want body and residual sweetness, try 1.0–1.1 qt/lb at 154–156°F. The calculator updates in real time as you change the ratio.
Always stir thoroughly when doughing in, then stir again at five minutes
Dry-spot temperature gradients in the grain bed can give a false reading immediately after doughing in. Stir the entire mash for at least 60 seconds to distribute heat, then check temperature. Check again at five minutes and stir once more before closing the lid for the rest. An accurate rest temperature reading requires a fully homogenized mash, not a reading taken at the surface of a freshly added water infusion.
Where to buy
Got your numbers? Here's where to pick up what you need:
The vocabulary of the mash — the terms that appear on recipe sheets, in brew software,
and on the calculator above — in plain English.
Strike water
The hot water you add to the grain to begin the mash. Because cold grain absorbs heat from the water, strike water must be heated above your target rest temperature by the amount the calculator computes. "Striking" refers to the act of adding this water to the grain.
Mash
The mixture of hot water and crushed grain in which enzymatic conversion of starches to fermentable sugars occurs. The liquid drained from the mash after conversion is called wort. A single-infusion mash rests at one temperature; decoction and step mashes use multiple temperatures.
Mash rest temperature
The temperature at which the mash is held during the saccharification rest — typically 148–158°F (64–70°C) for most ale and lager recipes. This temperature determines the balance of fermentable sugars (maltose) versus unfermentable dextrins and therefore the beer's final gravity and body.
Mash thickness (water-to-grist ratio)
The volume of strike water per pound of grain, measured in quarts per pound (qt/lb). A thicker mash uses less water per pound and concentrates enzymes; a thinner mash uses more water and improves enzyme mobility. Common range for homebrewing is 1.0–1.5 qt/lb.
Doughing in
The act of mixing strike water and grain together to form the mash. Consistent, thorough stirring during dough-in prevents dry spots and temperature gradients that produce inaccurate rest temperature readings.
Beta-amylase
An enzyme that cleaves maltose (a highly fermentable disaccharide) from starch chains. Most active at 131–150°F (55–65°C), it denatures rapidly above roughly 158°F (70°C). A mash resting at 148–152°F maximizes beta-amylase activity, producing a drier, more fermentable wort.
Alpha-amylase
An enzyme that randomly cleaves starch chains into a mix of fermentable sugars and unfermentable dextrins. Active across a broader range but peaking at 154–162°F (68–72°C). Higher mash temperatures favor alpha-amylase, producing fuller body and higher final gravity.
Attenuation
The percentage of fermentable sugars that yeast converts to alcohol and CO₂. High attenuation (a dry beer) results from a mash that produced mostly fermentable sugars; low attenuation (a full-bodied beer) results from more unfermentable dextrins. Both mash temperature and yeast strain affect attenuation.
Single infusion
A mashing method in which all strike water is added at once at a calculated temperature, and the mash rests at that single temperature for the entire saccharification rest — typically 45–90 minutes. The simplest and most common method for homebrewing with well-modified modern malts.
Sparge
The rinsing step that follows the mash. Hot water (sparge water, typically 165–170°F) is run through the grain bed after the first wort has drained to rinse residual sugars from the husks into the kettle. The sparge water calculation is separate from the strike water calculation; this tool covers strike water only.
Frequently asked
Strike water temperature is the temperature your brewing water must reach before you add it to the grain. Because cold grain absorbs heat from the water, the water must start hotter than your target mash rest temperature. If you add water at exactly your target, the grain chills it below that target and conversion suffers. The Palmer formula accounts for grain weight, grain temperature, mash thickness, and the specific-heat ratio of grain to water — giving you the correct starting temperature for the water so the mixture equilibrates right at your intended rest temp.
Mash thickness is the volume of strike water per pound of grain, measured in qt/lb. A thicker mash (1.0 qt/lb) concentrates enzymes and tends toward fuller body; a thinner mash (1.5 qt/lb) improves enzyme mobility and fermentability. Most homebrewers start at 1.25 qt/lb and adjust based on the style. Thicker mashes also require hotter strike water relative to grain temperature. The reference table on this page shows approximate rest temperatures and body outcomes for each thickness range.
The specific heat of water is roughly 1.0 BTU/lb/°F; dry malt grain is roughly 0.38 BTU/lb/°F. The 0.2 constant in the Palmer formula is an empirical approximation that accounts for the practical heat exchange in a typical homebrew mash system, including vessel absorption and wet grain. It gives a good starting temperature for most brewers — dial it in further by measuring your actual rest temperature over a few batches and noting the consistent error, if any, for your specific setup.
If the mash is too hot, add small amounts of cold water in half-quart increments, stir thoroughly, and re-measure before adding more. If it is too cold, add small amounts of boiling water the same way, or apply gentle direct heat if your mash tun allows it. In both cases, overshoot is easy — add slowly. For future batches, pre-heat the mash tun with hot water (discarded before doughing in) to remove vessel thermal mass as a variable, and measure grain temperature rather than assuming room temperature.
No. This calculator is specifically for a single-infusion mash where all strike water is added at once and the mash rests at one temperature. Decoction mashing removes and boils a portion of the mash to raise temperature — a separate calculation. Step mashing with a HERMS or RIMS system ramps temperature in the vessel without additional infusions. Infusion step-ups (adding boiling water to an existing mash) use a different formula. Use this tool for the most common homebrewing scenario: all-grain single infusion, batch or fly sparge.
The Palmer formula assumes the vessel is already at the same temperature as the grain. If your mash tun is a room-temperature cooler you have not pre-heated, it will absorb 1–3°F from the mash water, causing the rest to land slightly below your target. Pre-heating the vessel — fill with hot water, let sit a few minutes, discard, then dough in immediately — largely eliminates this. If you skip pre-heating, add 1–2°F to the calculator's result for your first few batches until you know your system's consistent error.
Both enzymes convert starch to sugars, but they produce different products. Beta-amylase produces highly fermentable maltose and is most active at 140–152°F (60–67°C) — a lower rest temperature produces a drier, more attenuated beer. Alpha-amylase peaks at 154–162°F (68–72°C) and produces a mix of fermentable sugars and unfermentable dextrins, leaving more body and mouthfeel. Most recipes target 150–156°F to balance both activities. Setting your mash rest temperature deliberately — rather than accepting wherever the mash lands — is the primary lever for controlling final gravity and body.
The arithmetic is exact for the inputs you provide — every formula is shown on this page. Accuracy of the predicted rest temperature depends on how well your inputs match your actual system. The 0.2 constant is an approximation; different grain bills, vessel materials, and ambient conditions introduce small errors. Most brewers find the formula gets them within 1–2°F on a well-insulated cooler tun. Treat the result as a starting point, measure your actual rest temperature after doughing in, and apply a consistent correction for your system across future batches.
Common mistakes with the strike water calculator
The infusion formula is well-proven, but the inputs brewers enter are often wrong. These are the most common reasons a mash lands 3–5 °F off target.
Assuming grain temperature equals room temperature
Grain stored in a cold garage or basement can be 10–15 °F colder than the room you're brewing in. Entering the ambient room temperature instead of the actual grain temperature is the single most common reason strike water comes out too cold. Take the grain temperature with a thermometer just before doughing in, not a guess.
Skipping the mash tun pre-heat
A room-temperature cooler mash tun absorbs 1–3 °F from the strike water before the grain even goes in. Rinse it with a gallon or two of very hot water, let it sit for two minutes, then dump that water before adding your strike water. The formula accounts for vessel heat absorption implicitly — if you skip the pre-heat, your rest temperature will fall short.
Not stirring thoroughly at dough-in
Dry spots and clumps create temperature gradients across the mash. If you measure temperature in one corner right after doughing in, you may be reading a pocket that is 2–4 °F different from the average. Stir thoroughly, then wait 60–90 seconds before measuring to let the temperature equalize.
Ignoring your system's consistent offset
If your actual rest temperature consistently runs 2 °F below what the formula predicts, that offset is real — it is your system's fingerprint. Don't keep re-entering the same inputs and expecting a different result. Adjust your grain temperature input by the offset amount on future batches, or note it as a system constant and add it to the target. Source: Palmer infusion mash formula, from John Palmer's How to Brew.