How to use the mash strike water calculator
- Choose your units: pounds, quarts and degrees Fahrenheit, or kilograms, liters and degrees Celsius.
- Enter the grain weight, the water to grain ratio (quarts per pound or liters per kilogram), the temperature of the grain and the target mash temperature.
- Optionally add some degrees for a cold mash tun, and adjust the heat constant in the advanced options.
- Read the strike water temperature, the volume of water and a check that mixing the water and grain gives the target.
Formula
strike temperature = (0.2 / R) x (target - grain temperature) + target
R is the water to grain ratio in quarts per pound
R in quarts per pound = liters per kilogram / 2.086351
water volume = R x grain weight
check: mash temperature = (R x strike + 0.2 x grain temperature) / (R + 0.2)
The 0.2 is a rule-of-thumb constant for the heat that dry grain absorbs compared with water. It works on any temperature scale, since only differences enter the formula.
Ten pounds of grain at 1.5 quarts per pound
With 10 pounds of grain at 68 degrees Fahrenheit, a ratio of 1.5 quarts per pound and a target of 152 degrees, the strike water temperature is (0.2 / 1.5) x (152 - 68) + 152 = 163.2 degrees. The water volume is 1.5 x 10 = 15 quarts, which is 3.75 gallons or 14.2 liters. Mixing 163.2 degree water with the grain gives (1.5 x 163.2 + 0.2 x 68) / 1.7 = 152 degrees, the target. Adding 3 degrees for a cold tun gives 166.2.
In metric, 4.5 kg of grain at 20 degrees Celsius, a ratio of 3.1 liters per kilogram and a target of 67 degrees means the ratio is 1.486 quarts per pound. The strike water is 73.3 degrees Celsius and the volume 13.95 liters.
Why the water is hotter than the mash
Cold grain soaks up heat from the water, so the water must start hotter than the temperature you want for the mix. The thicker the mash (the less water per pound of grain), the more the grain cools the mix, so a thick mash needs a hotter strike. The formula captures this with the ratio in the denominator.
Treat the answer as a starting point
A tun that starts cold takes heat from the mash, thermometers differ by a degree or two, and the heat of grain varies a little. Many brewers heat the tun first, stir the mash well, and measure. They then adjust with a little hot or cold water. Keep notes from each brew to refine the correction you enter for your gear. To follow the brew with the color and the strength, see the SRM Beer Color Calculator and the ABV Calculator.
More tools for brewing and the lab bench
For related work with brewing and solutions, try the SRM Beer Color Calculator, Hemocytometer Cell Count Calculator and Concentration Unit Converter.
Assumptions and limits
- The mash tun starts at the target temperature or you add the heat loss yourself.
- The grain is at one even temperature and the water is stirred well.
- The rule-of-thumb constant of 0.2 is close enough for dry malt.
- The ratio is in quarts per pound or liters per kilogram to match the units you chose.
- The grain weight, ratio and temperatures in the form are examples to replace with your own.
Frequently asked questions
What is strike water?
It is the hot water you add to the grain to start the mash. It is heated to a higher temperature than the target so that the mix settles at the right level once it meets the cooler grain.
What ratio should I use?
Brewers choose a ratio by their recipe and equipment, and it also changes the character of the mash. The tool takes your ratio as given and does not say which is best.
Does the formula work in Celsius?
Yes, because only the difference between the target and the grain temperature enters the formula. The ratio must still be converted to quarts per pound, which the tool does when you choose metric.
How do I find the heat loss of my tun?
Brew a few times with the tool and compare the temperature you read after mixing with the target. The average difference is the correction to enter, and it can be different for each tun.