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Low ABV on "High Gravity" 1 Gallon Black IPA Kit

I recently bottled the Black IPA (1 gallon extract kit: and am confused by the low potential ABV. My O.G. was about 1.047 and my F.G. was 1.022, giving me a potential ABV of about 3.3%. Given this is a high gravity kit, I expected something at least twice that. I’m now trying to diagnose what went wrong and would appreciate any suggestions.

I followed the recipe to the letter and everything seemed to be fine with the batch. It had a nice healthy fermentation at about 72-73 degrees.

I realize that’s not a lot of information, but these kits are pretty simple. Anyone have any thoughts or something I should consider that maybe I’m missing?

If you did a partial boil and topped off in the fermenter with water it can be very difficult to get a good gravity reading due to stratification of the liquids. In other words the water doesn’t mix quickly and evenly with the wort. So you get a bad gravity reading.

If you used all the ingredients and hit the volumes then your resulting wort should hit the predicted OG pretty closely.

Having said all that your FG also seems a bit high. Which yeast did you use? How long did you ferment? Did you transfer to a secondary? If so how long in primary?

Sorry just noticed it was a one gallon kit so some of these questions aren’t relevant. I looked back at when I brewed this kit a few years ago as extract. My OG was 1.058 and FG was 1.010 using US05.

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LME should provide 36 points per gallon. With 1.5 pounds of LME for 1 measured gallon in the fermentor, the OG should have been 1.054. The US-05 should have fermented the beer down to 1.010 or 1.011. I suspect a measurement error especially on the FG if you used a refractometer. Refractometers do not read accurately in the presence of alcohol.

If you are using a hydrometer for SG does it read 1.000 in distilled water at the calibration temperature, or rather close in tap water? The calibration temperature is printed on the card inside the hydrometer. Most hydrometers are calibrated for 60°F.

How long was the beer in the primary? There could be a problem with the fermentation finishing in the bottles if 1.022 for an FG was an accurate reading .

Any extra information will help diagnosing the problem.

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weird it could be the fermenting did not compleet stop yet did you use a yeast starter or dry yeast

This won’t be super helpful, but I just bottled this same 1 gallon kit 2 weeks ago. I haven’t taken gravity readings, but it’s definitely the highest ABV of any of the 1 gallon kits I’ve done.

Did you ferment in a 1 gallon carboy, a “Little Big Mouth Bubbler”, or a two gallon food grade pail? Did you “top off” the wort to “one gallon” in either the kettle or the fermenter? There is no ‘right’ or ‘wrong’ answer, but the answers could help with understanding why your OG is 1.047, rather than 1.054-ish

After step 7 (“Siphon the cool wort from the kettle into the jug”) did you have extra wort left in the kettle when the fermenter was full? Again, no right or wrong answer - just looking for places that might contribute to the lower OG.

Did you measure SG using a hydrometer or refractometer? Once again, no right or wrong answer, just trying to understand how the measurements were made.

I would be worried IF the reading was close to good, about bottle bombs… Just out of a safety factor, wrap/cover with an old blanket Sneezles61

Thanks everyone for the replies. I’ve responded to a few below.


I’m not sure what more to tell you beyond that I followed the recipe. This includes the full 45 minute boil prescribed in the instructions. I did not top off the fermenter with water - it wasn’t necessary since this was a small batch kit.

The kit did not come with a predicted O.G. so I’m not sure what is normal for the 1 gallon batch vice the 5 gallon batch of the same beer.


I did use a refractometer. I’m surprised to hear they are inaccurate in the presense of alcohol, particularly since Northern Brewer sells one (the one I used in fact) and they are hyped for their accuracy.

The beer was in the primary for about 17 days, which is three days longer than the recipe called for. Fermentation had definitely finished as far as I could tell.


I used a 1 gallon carboy as the fermenter. I did have extra wort in the kettle when the fermenter was full. I used some of this for a gravity reading and dumped out the rest.

I measured both the O.G. and the F.G. using a refractometer, specifically, this one:

Your SG is most likely lower than what the refractometer indicated. Links to calculators for correcting the refractometer reading.

I’ll bet your IPA finished where it should for US-05.

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The 5-gallon kit lists an OG of 1.075, so I assume your 1-gallon kit was designed to be the same. The fact that you had some wort remaining in the kettle after you filled the fermenter to the 1-gallon mark means you didn’t boil off as much as expected, so your OG was under the designed level,

Had you hit an OG of 1.075 and measured your final gravity at 1.022 (by refractometer), that translates to a specific gravity of 0.99. Not likely with US-05. With an OG of 1.047, your final gravity is actually 1.006.

I use a refractometer regularly and it is highly accurate for both unfermented and fermenting beer. You just have to adjust/correct the reading for fermenting beer because alcohol has a different refractive index than sugar water (wort). Don’t be discouraged with your refractometer. They are excellent tools, they just need to be shipped with better instructions.

I made a faulty assumption in my previous post: the instructions for the 1-gallon kit list 1.5 pounds of liquid extract plus 5 ounces of corn sugar. That puts the predicted OG at 1.047 before considering any contribution from the steeping grain.

It sounds like you did everything right and got blind-sided by incomplete information.

Looks like @flars, @sneezles61, and @old_dawg covered the topic well today.

When I brewed some one gallon kits, I would occasionally have some extra wort. A one gallon carboy, filled to the bottom of the “one gallon” letters is around 120 oz.

@flars and @old_dawg

Thanks for the help, my biggest concern was that I had done something wrong but it sounds like the measuring device was to blame. Definitely good to know going forward!

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