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How Big Does My Mash Tun Need to Be?


Note: all figures courtesy of Bobby_M from homebrewtalk.

So, you're new to all grain homebrewing, and you've got your eye on a sweet cooler to convert into that very first mash tun. You've looked at conversion plans, you know exactly what manifold/false bottom/braid solution you want to use. However, you aren't quite certain that your targeted cooler can accomodate the type of beer you want to brew.

The chart below comes in really handy for calculating the size cooler you'll need to use as a mash tun. The shape of the cooler doesn't really enter in to our figures below, though it's worth noting that the typical rectangular cooler setup normally gives you greater flexibility at a lower price point. The bottom line, though, is to make sure that you come up with an equipment setup that fits your brewing style and desires.

Mash Tun Size 5 gallon
(20 quart)
10 gallon
(40 quart)
13 gallon
(52 quart)
15.5 gallon
(62 quart)
Max grain capacity
(assuming 1.25 qt/lb)
12 lbs 24 lbs 31.2 lbs 37.2 lbs
Total strike water
(gallons)
3.75 7.5 9.75 11.625
Total combined volume
(gallons)
4.87 9.74 12.662 15.097
Max gravity units
(@ 70% efficiency)
295 590 767 914.5
Max OG, 5 gallon batch
(@ 70% efficiency)
1.059 1.118 1.153 1.183
Max OG, 10 gallon batch
(@ 70% efficiency)
1.030 1.060 1.077 1.091
Max gravity units
(@ 80% efficiency)
340 680 884 1054
Max OG, 5 gallon batch
(@ 80% efficiency)
1.068 1.136 1.177 1.211
Max OG, 10 gallon batch
(@ 80% efficiency)
1.034 1.068 1.088 1.105


So, by checking our numbers, we can see that a five gallon mash tun will allow us to brew five gallon batches of moderate gravity beers, but won't allow us to brew any big beers... or ten gallon batches of anything but the smallest of beers. A ten gallon mash tun, on the other hand, will allow us to brew five gallon batches of huge beers - up to and including a 1.100 barleywine, as well as a ten gallon batch of moderate gravity beer. Obviously, larger mash tuns give you even more flexibility in your brewing decisions; if you think that you may ever want to go to ten gallon batches (or brew big beers), you may well want to start with a large mash tun.



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