Calculations

28.1Brew day

• Hydrometer correction: a hydrometer reading taken warm, corrected to the 20 °C it's calibrated for. It uses a curve fitted to the ASBC's correction table for Plato hydrometers. Above 40 °C it still gives a number, but says the correction isn't confirmed that hot: cool the sample for an accurate reading.

Example: 15.4 °P read at 86 °C corrects to 24.44 °P — with a note to cool the sample.

• Liquor back: your gravity came out higher than the target. It tells you how much water to add, counted by the weight of the sugar in the wort so the beer lands on target.

Example: 1,300 L at 13.5 °P, target 12.5 °P: add 109.7 L.

• Short on gravity: your gravity is lower than the target before the end of the boil. It tells you how much water has to boil off and how many more minutes that is at your kettle's boil-off rate (from the equipment profile; if the profile has none, type it). Or use Sugar addition instead.

• Sugar addition: how much sugar brings the wort up to a target gravity. Sugar yield is 100 for ordinary sugar (sucrose); lower it for syrups or anything with water in it.

Example: 1.027 to 1.042 in 542.5 US gallons (2,054 L): 86.1 kg of sugar.

• Mash off temperature: the mash is too cold or too hot. Put in the mash water, the grain, the temperature now, the target and the temperature of the water you'll add: hot water to raise it, cold water to bring it down. If that water can't get there (too cool to raise it, too warm to lower it), it says so.

Example: 600 L of water and 200 kg of grain at 63 °C, target 65 °C, with 95 °C water: add 45.5 L.

• Refractometer: a Brix reading turned into gravity. Choose Wort for a reading before fermentation, or Fermenting or finished beer once it has started: alcohol throws a refractometer off, so then it needs the original reading too (Sean Terrill's correction). The wort correction factor is 1.04 as standard; measure your own refractometer against a hydrometer for the best figure.

• IBU → hop addition: how many grams of a hop give a target bitterness, using the IBU method chosen in Settings.

Example: 13.9 IBU from a 15.7% hop at 10 minutes, in 1.060 wort, 542.5 US gallons: 2.38 kg.

• Salt addition: what a salt adds to the water, in ppm of each ion — the same mineral table as the Water tab. Calcium chloride is the dihydrate; magnesium chloride is the flakes (dry にがり, nigari).

• Attenuation & ABV: apparent attenuation and ABV from the original and final gravity.

Example: 14.7 °P to 2.5 °P: 83.0% attenuation, 6.57% ABV.

• Carbonation: the regulator pressure for a carbonation level at a beer temperature, or the other way round. It follows the Zahm & Nagel CO₂-in-beer chart, at sea level, in gauge pressure, and answers in bar, kPa or psi.

Example: 2.5 volumes at 3.3 °C (38 °F): 0.78 bar (11.25 psi).

• Yeast cell count: count a slurry with a hemocytometer and methylene blue. Put how many of the 25 middle squares you counted (usually 5), the dilution (only the second number: 200 for 1:200), and the live (clear) and dead (dark blue) cells. It gives the live cells per mL and the viability, and warns under 85% viable. Leave the dead cells blank and it gives the live cells but says the viability isn't known yet; type 0 if none are dead. Then put the batch, the original gravity and the pitch rate, and it tells you how many liters of slurry to pitch.

Example: 220 live and 20 dead in 5 squares at 1:200: 2.2×10⁹ live cells per mL, 91.7% viable.

• Beer calories: estimated from the original and final gravity, per 100 mL (what a Japanese nutrition label states) and per 350 mL can.

28.2Conversions

Type in any box and the others follow.

• Weight: kilograms, grams, pounds and ounces.
• Volume: liters, hectoliters, milliliters, US barrels (31 gallons), US gallons, quarts, pints and fluid ounces.
• °F ↔ °C
• SG ↔ °P

Example: a recipe from overseas calls for 11 lb of Maris Otter. Type 11 in Pounds: it's 4.99 kg.