Mash water = grain weight × your chosen water-to-grain ratio + equipment dead space. Enter your own equipment values below, then follow the worked example to see where the result comes from.
[brewmybeer_calculator type="mashwater"]
Meet the three inputs
- Grain weight: the total grain going into the mash, in kilograms.
- Water-to-grain ratio: litres of water per kilogram of grain, selected for your recipe and equipment.
- Equipment dead space: additional water your equipment profile requires outside the grain bed. Enter zero when your method has no such allowance.
The ratio describes water in relation to grain. The final answer is water volume, not the combined volume of wet grain and water: you must check the vessel's mash capacity separately.
Try it: change one input
Suppose your planning inputs are 4 kg of grain, 3 L/kg and 2 L of dead space. The calculation is 4 × 3 + 2 = 14 L. If you increase the grain to 5 kg and leave the other inputs unchanged, the answer becomes 17 L. That extra kilogram adds 3 L of water in this example.
Quick challenge: what happens if dead space increases by 1 L?
The calculated mash-water volume increases by exactly 1 L. The grain ratio stays the same. Try the change in the calculator to check your answer.
Before measuring your water
Use the water-volume convention in your equipment instructions. A reading taken hot is not directly interchangeable with a reading taken cold. For multi-step infusion or decoction mashes, account for each addition rather than treating this single-infusion calculation as a complete water plan.
Next, work out the water needed for rinsing the grain with our sparge-water calculator. Keep recoverable equipment space separate from water genuinely lost during collection.
Method and source
The formula follows the single-infusion approach documented by Grainfather's mash and sparge water method. The example here is illustrative arithmetic, not a recommended mash ratio. This tool does not predict conversion, pH or beer quality.