Malt bills - Potential extract weight per volume of wort required for target gravity

Plato is just percentage by weight of extract in a solution, so you don't need a table. Any volume of wort at 12 plato is 12% extract by weight. So if you have 1 litre of it, 120g of it is extract. That's all you need.

I'm of the firm opinion that plato is the way to go, precisely because of this simplicity. The unit accounts for volume automatically, and being fully metric and decimal, is a breeze to use. No PPG, or sucrose contribution of 46ppg or any of that nonsense, just multiplying percentages.

10L @ 12P = 10 x 12% = 1.2kg extract conversely 9kg extract in 100L water = 9/(9+100) = .0825 = 8.25P

Pounds extract per barrel is actually quite straightforward to calculate. Here's my method:

• First you begin with the density of water. Water is ~8.34 pounds per gallon (depending on the temperature). Therefore a barrel is 258.5 pounds (31 gal.).

• You will need both °Plato and SG for the calculation, and it is sufficient to use the old rule of thumb 1°P = 1.004 SG (eg. 10°P = 1.040 SG, or 13°P = 1.052 SG, etc.).

• Since SG is just the density relative to water, you already know how much a barrel of wort (or beer or anything) will weight at any given SG. You just multiply the weight of a barrel (or any volume) of water by the SG (e.g. one barrel of wort at 12°P will weigh: 258.5 lb. x 1.048 SG = 270.9 lb., using the numbers mentioned above).

• Finally, pounds extract per barrel is as simple as multiplying the weight of a barrel of wort at your gravity (270.9 lb. at 1.048 SG) by °P expressed as a percentage (e.g. instead of multiplying by 12, you multiply by 0.12, which is the same as 12%). So, 270.9 lb. x 0.12 = 32.5 lb. extract per barrel (close enough if you ask me).

_{- Remember that, while you're using both Plato and SG for different parts of the calculation, they must equal one another.}

_{-The Plato scale simply expresses the level of extract (or dissolved solids) in a solution as a percentage of the total weight of the solution. This is why this method works}

_{-Why this isn't exactly the same as the tables? 1) For some reason the ASBC uses the weight of water at 32°F for their calculation; 2) The conversion from SG to plato is not exact (as mentioned in the other answer)}

After much more scouring of the web googling the question in various and sometimes outlandish ways I stumbled across the following forum thread from 2006 which appears to answer my question:

https://discussions.probrewer.com/showthread.php?4636-Extract-Tables

Someone provided a table for the degrees plato and lbs. extract per BBl and kgs extract per hl.

I have expanded is slightly and present the table here should anyone in the future require this knowledge.

Degrees    | Potential | kg Extract    | lbs. Extract | lbs. Extract     | lbs. Extract
Plato (°P) | Gravity   | per hL (100L) | per US BBL   | per Canadian BBL | per UK BBL
-----------------------+---------------+-----------------------------------------------
8            1.032     | 8.27          | 21.36          20.69              29.79
9            1.036     | 9.34          | 24.12          23.36              33.64
10           1.040     | 10.42         | 26.90          26.05              37.52
11           1.044     | 11.50         | 29.70          28.77              41.42
12           1.048     | 12.59         | 32.52          31.50              45.36
13           1.053     | 13.69         | 35.36          34.25              49.32
14           1.057     | 14.80         | 38.22          37.02              53.31
15           1.061     | 15.92         | 41.10          39.81              57.32
16           1.065     | 17.04         | 44.00          42.62              61.37
17           1.070     | 18.17         | 46.92          45.44              65.44
18           1.074     | 19.31         | 49.86          48.29              69.54
19           1.079     | 20.46         | 52.82          51.16              73.67
20           1.083     | 21.61         | 55.80          54.05              77.82
21           1.087     | 22.77         | 58.80          56.95              82.01
22           1.092     | 23.94         | 61.82          59.88              86.22
23           1.096     | 25.12         | 64.86          62.82              90.46
24           1.101     | 26.30         | 67.92          65.78              94.73
25           1.106     | 27.50         | 71.00          68.77              99.02
26           1.110     | 28.70         | 74.10          71.77              103.35
27           1.115     | 29.91         | 77.22          74.79              107.70
28           1.120     | 31.12         | 80.36          77.83              112.08
29           1.124     | 32.35         | 83.52          80.89              116.49
30           1.129     | 33.58         | 86.70          83.97              120.92

The potential gravity is calculated using the following formula*:

SG = 1 + ( plato / (258.6 – ( (plato/258.2) * 227.1) ) )

*https://www.brewersfriend.com/plato-to-sg-conversion-chart/