How do you calculate pre-boil gravity?

[hal simmons]

I'm doing my first AG batch this weekend. Below is the recipe i'm planning on using. I've got BeerToolsPro, but I can't figure out how to get it to tell me what my SG reading should be pre-boil? After I've sparged, I'd like to be able to tell if I'm where I should be at with the SG?


All-Grain ESB
8-C Extra Special/Strong Bitter (English Pale Ale)

Size: 6.0 gal
Efficiency: 65.0%
Attenuation: 74%

Original Gravity: 1.059 (1.048 - 1.060)
Terminal Gravity: 1.015 (1.010 - 1.016)
Color: 13.2 (6.0 - 18.0)
Alcohol: 5.7% (4.6% - 6.2%)
Bitterness: 42.49 (30.0 - 50.0)

Ingredients:
13 lbs Maris Otter Pale
1 lbs Munich Malt
14.0 oz Crystal Malt 60°L
7 oz Wheat Malt
2.5 oz Goldings (4.2%) - added during boil, boiled 60 min
1 oz Cascade (4.1%) - added during boil, boiled 30 min
1 oz Cascade (4.1%) - added during boil, boiled 1 min
WYeast 1335 British Ale II


Saccharification Rest - Rest: 60.0 min; Final: 155.0 °F
Sparge: 4.82 gal sparge @ 170.0 °F, 7.61 gal collected, 45.0 min; Total Runoff: 7.81 gal

 

[jds]

To hit 1.059 in 6 gallons requires 59 X 6 = 355 GU (Gravity Units)

Distribute those 355 GU in 7.81 gallons of water, you have 355 / 7.81 = 45.3 or a preboil gravity of about 1.045.

Right? Anyone? Bueller?

 

[celtic_man81]

The simplest way is to look on your hydrometer (if you don't have one, get one.) Look at the gravity units on it, then look at the sugar per liter (or pound). It should give you a pretty good idea of what you need. you might need to add more or less sugar depending on the brew type. The Final Gravity will differ from brew to brew. If you are talking about something totally different, then sorry, I'm somewhat new to this.

 

[Yooper]

I'm mathematically challenged, so I use Beersmith and it calculates my preboil SG for me. I rarely use it anymore, though, since I actually have a pretty consistent (but low) efficiency and hit my expected post boil sg within a point or two.

I don't know how Beertoolspro, but I would think it's there in the software somewhere! Can you preview a brewing sheet or checklist, and it should have the preboil sg somewhere on that.

 

[Blender]

Can't you just adjust your batch size to the pre boil volume and get your intended gravity? That is what I do in Promash.

 

[hal simmons]

I figured it out. There's a little pop-up that comes up when you mouse over your initial boil volume that tells you what the SG of that wort should be. And jds was right on it's giving me 1.045.

 

[nl724]

To hit 1.059 in 6 gallons requires 59 X 6 = 355 GU (Gravity Units)

Distribute those 355 GU in 7.81 gallons of water, you have 355 / 7.81 = 45.3 or a preboil gravity of about 1.045.

Right? Anyone? Bueller?

+1 for me. I have used this method many times. It also works to help figure out how much corn sugar or DME you can add, after mashing, to reach your desired Postboil OG

 

[Bobby_M]

Yeah, I like mousing over the Preboil volume to get the preboil grav. It's not intuitive at all and it's not really well documented (just like everything else in BTP).

 

[jayhoz]

In Beersmith there are two ways that I know of to get at the pre-boil gravity.

1) Adjust the Batch size field to your Pre-boil volume and look at the OG Estimate.
2) Use the dilution tool. Enter your batch size and expected SG. Adjust the volume to add field till the total volume field matches your pre-boil volume. The Final SG value is now your pre-boil gravity.