please explain my og and fg

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tservice

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tservice

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I had to have a friend read it for me. Because I can not see well enough to see what it is reading. So I don't know if it was read correctly or not.:( Is there a digital gravity reader out there, that is cost effective. That has easy to see display?
 

JollyIsTheRoger

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I am trying to understand what sg and fg tells me. My first batch sg is 1.50 the fg is 1.10. So please explain what all that means. I used a kit http://www.rebelbrewer.com/shoppingcart/products/Lawn-Jockey-Pilsner-Kit-(Extract).html if that matters. Oh just in case I have my terms mixed up sg is starting gravity, fg is final gravity. Please correct me if I am wrong. I can not wait to try it.:rockin:
Thanks guys!!!
SG usually stands for specific gravity which is what you measure any time you measure. Brewers will say OG for Original Gravity and FG for Final Gravity. What you are measuring is the amount of sugar that is in the liquid you are measuring. Water will basically have an SG of 1.000. You measure the OG before you ferment and will get a number somewhere between 1.030 and 1.120. The lower the number the less sugar that is in solution. The yeast eat those sugars to produce alcohol, so if we know how much they ate, we know how much alcohol there is. You take another SG reading after fermentation is complete(your FG) and that will tell you how much sugar is left, usually between 1.000 and 1.030. Knowing the difference in these two numbers will tell you how much alcohol is in your beer/wine/mead/etc. Some people use a really basic formula where you take the difference and multiply by 131. For example, if you had an OG of 1.045 and an FG of 1.010: 1.045-1.010= 0.035*131= 4.585 so your beer is 4.5%abv. There are better calculators than that online such as the one above that gives you an answer of 4.7% with the same numbers.
 

unionrdr

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I've seen about 8 different formulas out there. All give a different answer. I use the Cooper's formula of (OG-FG)/7.46 + .5= ABV%. So 1050-1010=40/7.46 + .5=5.86%. I wonder which of all the formulas out there is closest to the truth?
 

Golddiggie

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I've seen about 8 different formulas out there. All give a different answer. I use the Cooper's formula of (OG-FG)/7.46 + .5= ABV%. So 1050-1010=40/7.46 + .5=5.86%. I wonder which of all the formulas out there is closest to the truth?
I've noticed that BeerSmith 2.1.02 (the latest release) comes out with the same results as from RootTop Brew. IMO, being 1 or 2 points off isn't the end of the world. Granted, I'd rather have a more accurate result, but we're talking minor points (for most of us at least).
 

Sir Humpsalot

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SG usually stands for specific gravity which is what you measure any time you measure. Brewers will say OG for Original Gravity and FG for Final Gravity. What you are measuring is the amount of sugar that is in the liquid you are measuring. Water will basically have an SG of 1.000. You measure the OG before you ferment and will get a number somewhere between 1.030 and 1.120. The lower the number the less sugar that is in solution. The yeast eat those sugars to produce alcohol, so if we know how much they ate, we know how much alcohol there is. You take another SG reading after fermentation is complete(your FG) and that will tell you how much sugar is left, usually between 1.000 and 1.030. Knowing the difference in these two numbers will tell you how much alcohol is in your beer/wine/mead/etc. Some people use a really basic formula where you take the difference and multiply by 131. For example, if you had an OG of 1.045 and an FG of 1.010: 1.045-1.010= 0.035*131= 4.585 so your beer is 4.5%abv. There are better calculators than that online such as the one above that gives you an answer of 4.7% with the same numbers.
Ha! Goes to show you don't know what you are talking about! My Bourbon County Stout clone had an O.G. of 1.127! :cross:

j/k. Good explanation there.

To the OP: Most kits will be around 1.040 to 1.060 or so for OG. The only exceptions being the strong/expensive/unusual kits such as barleywines, IPAs, etc.
 

Golddiggie

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I had to have a friend read it for me. Because I can not see well enough to see what it is reading. So I don't know if it was read correctly or not.:( Is there a digital gravity reader out there, that is cost effective. That has easy to see display?
Digital readers are EXPENSIVE. It's actually a digital refractometer at around $135+. Even my high grade refractometers were less (each). IMO/IME, a refractometer is easier to read, and provides solid results. I know there are those that will argue about how it's only good for the OG, but with proper use (and using the tools to offset for the presence of alcohol) it can also be used post fermentation (or once it's started). There are plenty of other advantages to a QUALITY refractometer. AS with most things, you get what you pay for, so don't go for the cheapest one out there. At least not without looking thought ALL the reviews on it. Bobby_M sells a good one, for a first refractometer. :D
 
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zeg

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I think it's a safe bet that your OG was not 1.5. Honey has an SG of a bit over 1.4, so at 1.5 you're talking about something with a consistency more like tar than wort!

Another xG abbreviation I've encountered is TG in the place of FG. It means "terminal gravity."

For ABV calculation, I just use 131*(OG-FG), with the SG readings as real gravities (like 1.050) rather than points (like 50). This is very similar to unionrdr's equation above. For typical beer ABVs, I don't think the difference between the various formulae is enough to worry about---they probably agree better than the accuracy of the gravity readings. At higher ABVs, there is more deviation, but I suspect that which is more accurate probably depends on the beer content so there is not a single "best" answer.

So I just multiply by 131.
 
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