%FG = 80% (Fine Grain Extract Yield)

%M = 4% (Moisture)

G = 1 lb (mass of grain)

V = 1 gal (vol of water)

E = 100% (Mash efficiency - to make calculations easier)

%M = 4% (Moisture)

G = 1 lb (mass of grain)

V = 1 gal (vol of water)

E = 100% (Mash efficiency - to make calculations easier)

The mass of sugars M should be given by:

M = G * (%FG - %FG * %M / 100) / 100 * E

M = 1lb * (80% - 80% * 4% / 100) / 100 * 1 = 0.768 lb

M = 1lb * (80% - 80% * 4% / 100) / 100 * 1 = 0.768 lb

Into 1 gallon, the degrees plato (P) should be:

P = M / (8.34 lb/gal * V + M)

P = 0.768 lb / (8.34 lb/gal * 1 gal + 0.768 lb) * 100 = 8.43°P

P = 0.768 lb / (8.34 lb/gal * 1 gal + 0.768 lb) * 100 = 8.43°P

Now, given that 1 lb sugar in 1 gal yields 1.046, the SG should be:

SG = (%FG - %Meff)/100 * G * 46 pt*gal/lb * V * E / 1000 + 1

SG = 0.768 * 1 lb * 46 pt/(lb*gal) * 1 gal * 1 / 1000 + 1 = 1.0353

SG = 0.768 * 1 lb * 46 pt/(lb*gal) * 1 gal * 1 / 1000 + 1 = 1.0353

Now... the PDF at http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5091778 has a conversion table between Brix and SG. The interesting rows:

Code:

```
°P / SG @ 20°C / lb dissolved solids per Gal
8.4 / 1.03344 / 0.722
8.5 / 1.03385 / 0.731
8.8 / 1.03508 / 0.758
8.9 / 1.03549 / 0.767
```

Am I calculating °P wrong? It should be (sugar wt / total wt) and there are ~8.34 lbs per gallon water (8 lbs / gal gets closer, but is less correct).

For distilled water: http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html