Author Topic: IBU Calculations  (Read 5493 times)

Offline Tomgm14

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IBU Calculations
« on: October 22, 2016, 09:20:20 PM »

I have so far only brewed all grain, but today I wanted to knock something out quickly so I decided to to a small batch using DME (12L batch using 2kg light DME).

When I was formulating my recipe, I noticed that a "normal" amount of bittering hops didn't give me anywhere near the IBUs I was looking for. Secondly, when i moved the batch size to 23L, it gave me a much more expected IBU figure.

Can someone explain what's happening here? I'm probably missing some fundamental point re: utilisation, but I'd love to understand what's happening.

Here is my recipe for reference:

2kg Light DME
30g Bravo (60min, 15.8%AA)
20g Cascade (10min, 8%AA)
15g Cascade (W/P, 8%AA)

With the batch size set to 12L, Beersmith gives me 17.8 IBU, but when I set it to 23L, it gives me 54.8 IBU.


Offline MtnSoul

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Re: IBU Calculations
« Reply #1 on: February 18, 2017, 08:29:21 AM »
Something similar happened to me this morning when calculating IBUs for a small beer with only DME.

The DME seemingly took the utilization to 0 for some reason because when I took out all of the DME from the recipe - IBUs were appropriately high but when adding the DME back the IBUs went right back down to 0.

I PM'd Beersmith on this forum and will await an answer here.

Offline Lukon

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Re: IBU Calculations
« Reply #2 on: April 21, 2019, 07:10:48 PM »
I just downloaded BeerSmith 3 for iPad and started entering recipes for small 2 gallon batches using Mr Beer HMEs as published in the add-on. Once I got the equipment profile and batch size more or less dialed in, I found the IBU calculations were WAY OFF.

After some analysis, it looks like BeerSmith assumes a 1 lb can size and extrapolates the IBU of the extract accordingly to get their gal/lb IBU number.  The only solution for me at this point was to do the math and plug the right number in. I took the Mr Beer published IBU number, multiplied it by gallon batch size (2 in this case) and divided it by can weight of 1.87lbs. I plugged that number in, and BeerSmith happily gives me the correct numbers now.
« Last Edit: April 21, 2019, 07:15:16 PM by Lukon »