Homebrewing arithmetic for beer, wine, mead and cider: ABV and attenuation, refractometer and hydrometer readings, mash water, IBU, colour and carbonation.
The numbers of a brew day worked from published formulas: alcohol and attenuation from your gravity readings, a refractometer reading corrected once alcohol is present, a hydrometer read at the wrong temperature, strike and sparge water, efficiency, dilution and boil-off, bitterness by the Tinseth formula, colour by the Morey equation, the sugar a mead or wine needs, and the priming sugar or keg pressure for the carbonation you want. Each page names its source, your equipment’s figures replace every default, and nothing here covers distilling or the effects of alcohol on health.
Alcohol by volume and by weight from original and final gravity, by the Hall formula and the linear one, with apparent and real attenuation.
You get: ABV by Michael Hall’s formula and by (OG − FG) × 131.25, ABV by weight, apparent and real attenuation, real extract, and both gravities in SG and °Plato — entered in either.
Open ABV & Attenuation CalculatorCorrect a hydrometer reading taken warmer or cooler than its calibration temperature, from the density of water (Tanaka 2001), in °F or °C.
You get: The corrected specific gravity, how many points the temperature moved it, the corrected °Plato, and both temperatures in °C — for samples between 0 and 40 °C.
Open Hydrometer Temperature CorrectionBrix to gravity for wort with your correction factor, and final gravity and ABV once alcohol is present, by Sean Terrill’s correction.
You get: Original gravity from a wort reading and your wort correction factor, and once fermentation has started the true final gravity by Terrill’s cubic, the ABV and attenuation — with what the uncorrected reading would have said.
Open Refractometer Calculator (Brix to Gravity)How much table sugar or honey raises a must, juice or wort to a target gravity — for mead, wine chaptalization and cider — with the volume it adds.
You get: The sugar or honey to add in kilograms and pounds, the volume after it dissolves, and the potential ABV if the must ferments to the final gravity you expect.
Open Sugar & Honey for a Target GravityBrewhouse or mash efficiency from a grain bill and a measured gravity, the gravity to expect at your efficiency, and the grain needed for a target OG.
You get: Efficiency against the grains’ potential, the most the grain bill could give, the original gravity to expect at an efficiency, the factor that scales the grain bill to a target gravity, and each grain’s share.
Open Brewhouse Efficiency & OGWater to add to lower a wort’s gravity, or how long to boil to raise it, and the gravity after a boil — by conserving gravity points.
You get: The volume that gives your target gravity, whether that means adding water or boiling it off and for how long at your boil-off rate, or the volume and gravity after boiling for a set time.
Open Dilution & Boil-Off GravityTotal brewing water, strike and sparge volumes worked back from the fermenter: boil-off, kettle losses, grain absorption and dead space are yours.
You get: Total water for the brew day, strike water for your mash thickness, sparge water, the pre-boil volume, and a line-by-line budget of every loss — in gallons and pounds or litres and kilograms.
Open Mash & Sparge Water VolumesStrike water temperature and volume for a single-infusion mash, and the boiling water a step infusion needs, by John Palmer’s equations.
You get: How hot the strike water must be to settle at your mash temperature, how much of it for your water-to-grain ratio, and for a step mash the water to add at a given temperature — in US or metric units.
Open Strike Water & Mash InfusionBeer colour in SRM and EBC from the grain bill by the Morey equation, with malt colour units and each grain’s share of the colour.
You get: Estimated colour in SRM and EBC, the malt colour units behind it, and how much of the colour each grain gives — from weights and °Lovibond, in pounds and gallons or kilograms and litres.
Open Beer Colour Calculator (SRM & EBC)Bitterness in IBU from your hop additions by Glenn Tinseth’s formula: amount, alpha acid and boil time, with batch volume and boil gravity.
You get: Each addition’s utilization and IBU, the total bitterness, and the bigness factor for your boil gravity — in ounces or grams, gallons or litres, with Tinseth’s calibration constant adjustable.
Open IBU Calculator (Tinseth)Regulator pressure to force-carbonate a keg to the volumes you want at the beer’s temperature, corrected for altitude, or the carbonation a setting gives.
You get: The gauge pressure in psi and bar for your target carbonation and beer temperature, or the volumes of CO₂ a regulator setting will give — with the air pressure at your altitude that the gauge reads against.
Open Keg Carbonation PressureCorn sugar, table sugar or another sugar for bottle carbonation, from the CO₂ already in the beer (Henry’s law) and fermentation chemistry.
You get: The priming sugar in grams, ounces and grams per litre, the CO₂ the beer already holds from fermentation, and the CO₂ the sugar must add — for the carbonation you choose, in volumes.
Open Priming Sugar Calculator