How to calculate OG

[LuNchBoX1371]

So im a new brewer and was wondering when i do my first all-grain how do i calculate my OG; because i am on brewers friend and it says to calculate my boil off i need to know my OG, how do i do that? I know how to calculate the OG for and extract recipe (its just pounds of extract times yield points,which is generally 40, divided by boil volume) but how do i get it for an all-grain; im reading john j palmers book how to brew and im about to re-read that section but just wanted to get clarification.

 

[thadass]

Many of us use software like BeerSmith or a website homebrew recipe calculator like http://www.brewtoad.com/ which can calculate OG. I don't know the hard math for it; I've just used the easy tools.

 

[progmac]

instead of using 40, use 37*expected efficiency. a good starting point for efficiency is 70%. so 37*.7 = 26ppg

so to get something with an OG of 1.052, you need two pounds of grain per gallon. (26*2=52)

it's super important to determine what kind of efficiency your system gives you. efficiency goes up or down depending on grain crush, number of sparges, type of sparging (fly or batch or none), mash thickness (1.25 qts/lb is a typical starting point), and so forth.

what's your equipment setup?

 

[gr8shandini]

One of our members here, BobbyM has a great article that cleared up a lot of questions I had even after reading Palmer:

http://www.suebob.com/brew/Bobby_Mallgrainprimer.pdf

The main difference between all-grain and extract is that you'll need to apply an efficiency factor to the theoretical points/lb/gallon for the malt you're using. That number is different for everyone, but if you have one of the more common setups, you can get a good estimate by looking at what other people use. I have an igloo cooler and typically use a single batch sparge and get about 70-75% efficiency. Grain crush is important, too. If you don't have your own mill, expect as bad as 60% from a LHBS's machine.

However, you don't need to do any OG calculations to get your boil off. Most recipes are either going to be either 60 or 90 minute boils. To get the boil off volume, you simply multiply the time by your boil off rate which is more or less fixed based on your system. The only way to figure it out is to boil some water in your kettle and see how much you have left after 30 minutes or an hour. You want a good visible boil rather than just a simmer, but you don't have to get too crazy about it and just go full-bore on your burner. If you measure your boil-off rate at a slightly more vigorous boil than you would normally use, it gives you a way to adjust your boil off slightly in case of an over or undershoot of your pre-boil gravity.

So, basically, for most recipes you'll know that you'll need to collect, say, 7 gallons of wort to get 5.5 after the boil and from that and the efficiency, you can calculate your OG.

 

[LuNchBoX1371]

instead of using 40, use 37*expected efficiency. a good starting point for efficiency is 70%. so 37*.7 = 26ppg

so to get something with an OG of 1.052, you need two pounds of grain per gallon. (26*2=52)

it's super important to determine what kind of efficiency your system gives you. efficiency goes up or down depending on grain crush, number of sparges, type of sparging (fly or batch or none), mash thickness (1.25 qts/lb is a typical starting point), and so forth.

what's your equipment setup?

My equipment set up is gonna be a 5.5 gallon brewpot and a 3 gallon brewpot. I am gonna get a 5 gallon igloo home depot cooler and start doin 3 or 1 gallon recipies with all-grain. Ok i get the 37 X Expected Efficiency. But how do you calculate efficiency in all-grain? And y do i use 37, or 40, when im doin and an all-grain in my formula when i thought the 40, or 37, was the yield points for extract and not for all-grain. And how would i start my recipe with a certain OG and figure out the grain bill from there, cause it sounds like you know lol

 

[gr8shandini]

Each grain is going to have its own value for the maximum potential extraction. Here's the tables that go into the Beersmith software:

http://www.beersmith.com/Grains/Grains/GrainList.htm

Under the column for "Potential SG", you'll see what they expect for a theoretical 100% efficient mash of 1 lb of grain in 1 gallon of water. For 2-row, it's 1.037 (or 37 points/lb/gallon). For flaked barley, it's 1.032, and for roasted barley, it's only 1.025.

So, if you wanted to make a typical stout (70% 2-row, 20% flaked barley, 10% roasted barley), you would calculate as follows:

[(7 lbs 2 row * 37ppg)+(2 lbs flaked barley * 32ppg)+(1 lb roasted barley * 25ppg)]/5 gallons = about 70 points

If you assume you have 70% efficiency, multiply that by .7 and you get 1.049.

Of course you may not get 70% efficiency. Or you may get quite a bit more. You're going to have to do some test runs to find out. I suggest making something fairly forgiving your first time out. Perhaps an IPA. If you don't go too crazy with the IBUs, if you miss low, just call it an APA. If you miss high, call it an "Imperial". Either way, you'll have something you can drink, and more importantly, you'll know what the efficiency of your system is for future brews.

I'd also highly recommend getting a refractometer. It makes it very easy to take the SG of your runnings and the pre-boil gravity. Even when you've got your system "dialed in" it's not unusual to be off by a point or three. If you can get a good pre-boil gravity, it's pretty easy to get a new final batch volume at the intended gravity. The you can adjust your boil time or intensity of the boil to make those minor corrections.

And finally, some brewing software is probably a good idea. It's good to know how it all works on paper, so I applaud you for making the effort. However, if something goes awry on brew day, having some software at the ready makes it a lot easier to make adjustments on the fly.

 

[LuNchBoX1371]

OOOOOOO OK i get it now thanks for all the help sorry i was a pain.Now that 1.049 is my BG and my OG or just my OG, or r they the same thing pretty much right? And then the more you boil-off the higher you OG rises in the calculator on brewers friend ok cool thank you. But one last thing is the volume you divide by is that your batch size or just your boil size?

 

[gr8shandini]

No problem. The the nice thing about doing this calculations is that the top number is basically the amount of sugar you've extracted from the grain. It doesn't boil off, so the volume you divide by is whichever one you need. If you want OG, use the batch size. If you want pre-boil, use the batch size + your expected boil off.

I haven't used brewer's friend, so I'm assuming BG means "boil gravity". That's going to be used to determine your hop schedule. I believe that most software uses the mid-point between the OG and the gravity at your first hop addition (based on your boil-off rate) to get an average value. However, unless you're doing a huge reduction to get a really high OG, the difference between using that average and just OG is only going to be a couple of IBU here or there. If I were doing things by hand, I'd just use OG.

 

[progmac]

My equipment set up is gonna be a 5.5 gallon brewpot and a 3 gallon brewpot. I am gonna get a 5 gallon igloo home depot cooler and start doin 3 or 1 gallon recipies with all-grain. Ok i get the 37 X Expected Efficiency. But how do you calculate efficiency in all-grain? And y do i use 37, or 40, when im doin and an all-grain in my formula when i thought the 40, or 37, was the yield points for extract and not for all-grain.

37ppg (or close, depending on the grain) is the max possible yield. in practical terms you don't get the max. if you're able to get 26ppg, then you have achieved 70% efficiency (37 * .7 = 26). this is typical and it is reasonable to assume 26ppg for your batch.

with extract, you get all the available sugars. you don't leave anything behind like you do with all-grain. so if dry extract is 40ppg, that's what you get. there is no efficiency conversion.

from this you can also deduce a conversion. 26ppg / 40ppg = 0.65, so you know that you can convert a recipe that might say 5 lbs DME to (5 * 1/0.65) lbs grain.

 

[LuNchBoX1371]

So i think im not getting it now because i added up all the ppg and pounds of grain and it came out to 418,905 as my ppg so something is not right

 

[freisste]

Are you putting 10,000lbs of grain into a single gallon of beer? Just kidding.

Take your ppg (usually mid 20s to about 40). Multiply by pounds. Divide by gallons.

If you are using multiple grains, it is ppg*lbs + ppg*lbs + ... Take the sum of all of those and divide by gallons.

 

[progmac]

example

10 pounds 2-row 37 ppg
70% efficiency
5 gallon batch

(10 * 37 *0.70) / 5 = 51.8, translates to OG of 1.0518

 

[LovesIPA]

First - OG is not calculated. It is measured. If you're using extract, you can come close to estimating it because using extract means all the sugar in the extract goes into the wort - there is no efficiency to factor in.

In all-grain, none of this is possible. How well the grain is crushed is the biggest factor in efficiency and there are many more less important ones. You absolutely cannot - as someone else here advised - look at other people's equipment setups and guess what your efficiency will be. You will be WILDLY inaccurate.

You have to measure your OG with a hydrometer, enter in the grain bill (Brewer's friend has a calculator on their site, BeerSmith has one built-in) and determine your efficiency from those numbers. It is always better to use pre-boil gravity and volume measurements. Your efficiency calculations will be more accurate, although it's possible to use your post-boil numbers as well.

Efficiency is based on the potential points per lb of grain per gallon. Some grain types have higher extraction potential than others. This is why the grain bill is important.

 

[progmac]

well, you've got to start somewhere so you know how much grain to buy. 70% should get you close. your gravity might swing 6 points either direction. maybe more if you double crush, biab, and stir like a madman.

 

[gr8shandini]

. . . You absolutely cannot - as someone else here advised - look at other people's equipment setups and guess what your efficiency will be. You will be WILDLY inaccurate.
. . .

First, let's not be pedantic. I'm sure the OP is well aware that he's talking about calculating an intended yield from a recipe and not an iron-clad guarantee of what the OG is going to be.

And to that end, you have to start somewhere, don't you? If you know for example, that you're going to do BIAB using grains crushed by your LHBS, you can probably get a pretty good guess at your efficiency based on what others are getting. If you're using an eHERMS, crushing your own in a 3 roller mill set to .039", and fly sparging, you might want to start by looking at what sort of efficiency folks with that sort of setup are seeing.

I'm pretty sure everyone here has said that he's going to have to do some test runs to figure out what his efficiency is for his system.

 

[LuNchBoX1371]

example

10 pounds 2-row 37 ppg
70% efficiency
5 gallon batch

(10 * 37 *0.70) / 5 = 51.8, translates to OG of 1.0518

Ok so its (pounds of grain) X (ppg) X (Efficency)/ (batch size) = OG. I was told that it was just (pounds of grain) X (ppg) = OG not multiplying the efficency. I did some calculations with my recipe (shown below) and i got within .002 of the calculated OG on Brewers Friend so i think its right

 

[LuNchBoX1371]

.You have to measure your OG with a hydrometer, enter in the grain bill (Brewer's friend has a calculator on their site, BeerSmith has one built-in) and determine your efficiency from those numbers. It is always better to use pre-boil gravity and volume measurements. Your efficiency calculations will be more accurate, although it's possible to use your post-boil numbers as well.

Efficiency is based on the potential points per lb of grain per gallon. Some grain types have higher extraction potential than others. This is why the grain bill is important.

So i test the OG before its boiled with a hydrometer to get the OG? Is it just the reading from the hydrometer? And pre-boiled gravity is just what it says on the hydrometer. But thats what im trying to figure out here is the effiency formula to calculate the OG.

 

[Oginme]

pound of grain x ppg gives you total potential gravity points. Efficiency takes into account what is left behind, since not all the sugars are extracted out.

To get efficiency you take the actual gravity points achieved and divide it by the total potential gravity points which can be obtained.

 

[LuNchBoX1371]

Take your ppg (usually mid 20s to about 40). Multiply by pounds. Divide by gallons.

If you are using multiple grains, it is ppg*lbs + ppg*lbs + ... Take the sum of all of those and divide by gallons.

The number comes out to 1,692,343.3 on my calculator so what am i doin wrong, or do i just need to multiply by the the efficency like the other guy said. Here is my recipehttp://www.brewersfriend.com/homebrew/recipe/view/88799/detroit-spiced-blonde-ale

 

[gr8shandini]

So i test the OG before its boiled with a hydrometer to get the OG? Is it just the reading from the hydrometer? And pre-boiled gravity is just what it says on the hydrometer. But thats what im trying to figure out here is the effiency formula to calculate the OG.

I honestly don't know what he's talking about with the pre-boil number being more accurate. The pre-boil gravity is going to be less than the OG. You really want to measure both, since you have an opportunity to correct back to your intended OG by calculating a new batch size and adjusting your boil accordingly.

But to get the true OG, you simply measure the wort before it goes in the fermenter. By the way, I'd also recommend getting a refractometer. That way, you only need to cool a couple of drops of liquid to take a sample rather than a few ounces. Makes brew days much less of a hassle.

 

[gr8shandini]

The number comes out to 1,692,343.3 on my calculator so what am i doin wrong, or do i just need to multiply by the the efficency like the other guy said. Here is my recipehttp://www.brewersfriend.com/homebrew/recipe/view/88799/detroit-spiced-blonde-ale

Got a "permission denied" from that link. If you just post up the recipe you're trying to make, we can walk you through it.

 

[LuNchBoX1371]

I honestly don't know what he's talking about with the pre-boil number being more accurate. The pre-boil gravity is going to be less than the OG. You really want to measure both, since you have an opportunity to correct back to your intended OG by calculating a new batch size and adjusting your boil accordingly.

But to get the true OG, you simply measure the wort before it goes in the fermenter. By the way, I'd also recommend getting a refractometer. That way, you only need to cool a couple of drops of liquid to take a sample rather than a few ounces. Makes brew days much less of a hassle.

Ok i'll look into a refractometer thank you

 

[LuNchBoX1371]

Got a "permission denied" from that link. If you just post up the recipe you're trying to make, we can walk you through it.

My Estimated OG is 1.040
Estimated FG is 1.010
My Grain and Grain bill is:
3 pds pale malt 60%
1 pd pilsner malt 20%
.5 pd crystal 10 L 10%
.5 pd flaked rye malt 10%
Boil Size: 3.7
Batch Size 3
My expected efficency is 65% since this is my first time doin all-grain and that efficency is what im calculating in my calculations

 

[gr8shandini]

OK, now we're getting somewhere. If we go back to the chart,

http://www.beersmith.com/Grains/Grains/GrainList.htm

It looks like we have:

3 lbs of pale malt @ 37 points/lb/gallon = 111 point-gallons*
1 lb Pilsner @ 36 ppg = 36 p-gal
.5 lb crystal 10L @ 35 ppg = 17.5 p-gal
.5 lb flaked rye** @ 36 ppg = 18 p-gal

For a grand total of 182.5 point-gallons. However, you only think you'll be able to extract 65% of that so you multiply 182.5*0.65 to get 118.6 point-gallons that will actually make it to the kettle.

From there, you just divide by your volumes and round to the thousandths

Pre-boil = 119 point-gallons / 3.7 gallons = 32.1 points = 1.032

OG = 119 p-gal / 3 gal = 39.6 points = 1.040


*I played with the units here a bit to make them make more sense. "Points per pound per gallon" is actually more like points / (pound / gallon). Another way to divide by a quantity is to multiply by its inverse, so you get points*(gallon/pound). Then when you multiply by a weight and divide by a volume, you're just left with points. If that's too confusing, just disregard and pay attention to the operations involved.

** your recipe calls for "flaked rye malt", but typically flaked grains aren't malted. So you're probably looking for "flaked rye" or "rye malt" - they're a bit different, so make sure you know what you want. Also, both tend to really gum up a mash. You don't have a ton here but any higher percentage and I'd consider using some rice hulls to keep things flowing.

 

[LuNchBoX1371]

Ok so you mulitply pounds of grain times ppg and then after the sum of all your grain has been added together divide by the batch size. If u add and multiply them all together and divide by the batch volume it comes out to the hundres of thousands. But i think im gonna go with the (pounds of grain) X (the ppg) X (efficency) = OG that seems pretty good but i like your math

 

[gr8shandini]

Almost there. You still have to divide by the volume (batch size for OG).

Unfortunately, as you can see, it's hard to write out equations in a text format. Now that you've mostly got the hang of it, go back and read the efficiency section of BobbyM's primer that I linked to. It should all make a lot more sense.

 

[freisste]

The number comes out to 1,692,343.3 on my calculator so what am i doin wrong, or do i just need to multiply by the the efficency like the other guy said. Here is my recipehttp://www.brewersfriend.com/homebrew/recipe/view/88799/detroit-spiced-blonde-ale

I took a finance class a while ago where we were taught time value of money. That has no bearing here, except that I was taught to use a financial calculator. For whatever reason, it was the only calculator I ever encountered that did NOT follow order of operations. If you have a financial calculator, it may be your issue. You could try using a real calculator or doing it one step at a time and using pencil and paper to keep it all straight with the formulas. As was said, they can be difficult to write in text from.

A "real" (I'm an engineer) calculator will tell you 10*10+10*10=200 while a piece of **** b-school calculator will tell you 10*10+10*10=1100...INCORRECT!

Good luck.

 

[LovesIPA]

First, let's not be pedantic. I'm sure the OP is well aware that he's talking about calculating an intended yield from a recipe and not an iron-clad guarantee of what the OG is going to be.

You're sure the OP is well aware? Because he posted a thread asking how to calculate OG? That's an absurd assumption frankly.

I'm not digging on OP at all - we all started somewhere. For a good laugh, look at my first posts. I was clueless when I started but I read a ton and have a pretty good handle on some - not all by far - of this stuff now.

And to that end, you have to start somewhere, don't you? If you know for example, that you're going to do BIAB using grains crushed by your LHBS, you can probably get a pretty good guess at your efficiency based on what others are getting. If you're using an eHERMS, crushing your own in a 3 roller mill set to .039", and fly sparging, you might want to start by looking at what sort of efficiency folks with that sort of setup are seeing.

That sounds like a lot of research to do to figure out a number that will undoubtedly be wrong anyway. You want a baseline, pick 70%. No need to go looking into what others are getting with their setups IMO. You're just wasting your time.

Ok so its (pounds of grain) X (ppg) X (Efficency)/ (batch size) = OG. I was told that it was just (pounds of grain) X (ppg) = OG not multiplying the efficency. I did some calculations with my recipe (shown below) and i got within .002 of the calculated OG on Brewers Friend so i think its right

You are solving for efficiency - everything else is measured or known. You don't solve for OG. Your efficiency is the variable. It will even change from batch to batch. You can estimate what it will be, but you won't know what it really is for a batch until you measure the volume of pre-boil wort and take a gravity sample.

Again - you don't calculate OG.

So i test the OG before its boiled with a hydrometer to get the OG? Is it just the reading from the hydrometer? And pre-boiled gravity is just what it says on the hydrometer. But thats what im trying to figure out here is the effiency formula to calculate the OG.

You don't calculate OG! You measure it with a hydrometer.

When you're just getting started, it's not necessary (IMO) to understand how efficiency is calculated. Use this calculator: http://www.brewersfriend.com/brewhouse-efficiency/

Enter in the pre-boil volume, grain bill, and pre-boil gravity, and it will tell you what the efficiency is. For your first few all-grain brews I would not even bother with figuring it out. Focus on the basics - your process, sanitation, etc. before getting wrapped up in how much sugar you're getting from the grains.

I honestly don't know what he's talking about with the pre-boil number being more accurate.

The pre-boil numbers are going to be more accurate for efficiency calculation purposes than post-boil numbers. There is more wort volume and therefore a higher degree of accuracy in the gravity reading.

You really want to measure both, since you have an opportunity to correct back to your intended OG by calculating a new batch size and adjusting your boil accordingly.

You can't understand why pre-boil gravity is more accurate, but you're going to post this and pretend it makes sense? What does "adjust your boil" even mean?

I realize exactly how I'm coming across, but you are starting to get under my skin with your snide and ill-informed comments.

By the way, I'd also recommend getting a refractometer. That way, you only need to cool a couple of drops of liquid to take a sample rather than a few ounces. Makes brew days much less of a hassle.

Refractometers are cool, but they are unnecessary and don't add a thing to the hassle factor IMO. People have been brewing for years without one and get along just fine. It's a very low item on mine and a lot of others' brewing wish list.

 

[gr8shandini]

Dude. Chill out. I wasn't trying to attack you. It's common to say that one is "calculating the OG" for a recipe when they're talking about coming up with a grain bill that they hope will yield an intended OG. What do you propose we call that?

Secondly, your assertion that hydrometer readings for the pre-boil volume are more accurate is patently false. Your hydrometer is as accurate as it's going to be as long as it's floating freely. In fact, you could argue the opposite of your stance since a hydrometer accurate to +/-1 point could be off by 2.5% in a 40 point solution but only 2% in a 50 point wort. Of course, the difference is too little to worry about, so we don't.

And finally, "adjusting your boil" simply means adjusting the time and/or intensity of the boil to achieve a different batch volume than originally intended. For example, you're expecting a 5 gallon batch of 1.050 beer with a 60 minute boil and a 1.5 gal/hour boil-off rate. Your expected pre-boil gravity in this case is 1.038. But for whatever reason, your 6.5 gallons of runnings only clock in at 1.036 today. You could follow your normal process and get 5 gallons of 1.047 beer, or you could shoot for 4.7 gallons of your intended 1.050 beer by boiling for an extra 12 minutes.