Basics and units
Mash volume
Before you add the malt, find out whether the tun will overflow. The tool adds up the water and the space taken by the grain.
Result
Fill in the values and run the calculation, or try the example.
This is the calculation Krausi uses. Create an account to save it in a recipe or a brew.
Create my accountWhy calculate the mash volume?
Grain does not vanish in water: it takes up space. With 5 kg of malt in 15 L of water, the tun holds much more than 15 L. An overflowing mash is a classic first-brew mistake, as is a tun that is too big and loses its heat.
This calculation is used to size the mash tun before buying one, or to check that a recipe found elsewhere fits your equipment. It is also the volume you need to correct a temperature by adding water or for a decoction.
How is the mash volume calculated?
The mash volume is the sum of the water and the volume taken by the grain:
V = water + absorption × grainWith the cautious value of 1 L per kilo of grain, 15 L of water and 5 kg of malt take up 20 L. Wet grain actually takes up 0.67 to 0.8 L per kilo: with 0.7 L/kg, the same mash is 18.5 L. Keep 1 L/kg if you want to be sure not to overflow.
Worked example
Values entered
- Mash water in litres: 15
- Grain weight in kg: 5
- Coefficient in L per kg of grain: 1
Result from the tool
- Mash volume in litres
- 20 L
What the tool does not do
- The approximation is linear: it does not account for how fine the crush is.
- It does not count the volume added by a decoction or a water addition during the mash.
- Leave some headroom to stir without splashing.
Frequently asked questions
What mash tun for 5 kg of malt?
With a ratio of 3 L of water per kilo, 5 kg of malt and 15 L of water take up about 20 L. A 25 to 30 L tun leaves the headroom needed for stirring.
How much space does grain take up in water?
One kilo of crushed malt takes up 0.67 to 0.8 L once wet. The tool suggests 1 L/kg by default, a deliberately cautious value.
And with the assistant?
Ask Krausi the same question in plain language: he picks this tool, does the calculation and files the result in your project.
Will 6 kg of malt and 18 L of water fit in my 27 L tun?
Yes: the mash will take up about 24 L with the cautious value of 1 L per kilo of grain. You have 3 L of headroom left for stirring.