Wine ABV Calculator

Winemakers are the biggest refractometer users, and wine is the beverage where the refractometer fails hardest after fermentation. Must at 22 Brix reads accurately. A finished dry wine at 13 percent alcohol reads around 7 to 8 Brix on the same instrument, which looks like a stuck fermentation when the wine is actually bone dry. The refractometer mode corrects the final reading using your original Brix. Above about 14 percent the correction itself becomes uncertain, so confirm any final gravity on a hydrometer before deciding on sweetness or fortification.

The hydrometer mode needs temperature correction less often than beer, because must and wine are usually read at cellar temperature, but a warm crush day or a heated red fermentation can put the sample 10°C above calibration, which is 0.002 to 0.003 of gravity. Enter the sample temperature and the calculator adjusts both readings.

The full Terrill correction and the hydrometer temperature polynomial, with their references, are on the general fermentation ABV calculator. For the reasoning behind temperature correction see hydrometer temperature correction.

Worked example. A red must starts at 1.092 and the finished wine reads 0.994 at 20°C. Balling gives 76.08 × (1.092 − 0.994) ÷ (1.775 − 1.092) = 10.92 percent alcohol by weight, and 10.92 × 0.994 ÷ 0.794 = 13.7 percent ABV. The simple 131.25 estimate says 12.9 percent, almost a full percent low, because that shortcut was tuned for beer-strength fermentations. Apparent attenuation is 0.098 ÷ 0.092 = 107 percent, a normal figure for a dry red.

Grape must contains almost no unfermentable dextrin. Wine yeast can consume nearly all of the available sugar, so a dry wine ferments far closer to completion than a beer does.

Once the sugar is gone, what remains is mostly water and ethanol. Ethanol is less dense than water (a specific gravity of about 0.789), so a dry wine routinely finishes below 1.000, commonly between 0.990 and 0.996. A hydrometer reading under 1.000 is normal here, not a fault.

Typical range: original gravity 1.080 to 1.100, final gravity 0.990 to 0.996. Because apparent attenuation is calculated against a final gravity below 1.000, wine can show an apparent attenuation above 100%, which is a quirk of the arithmetic rather than an impossible fermentation.

One caution on accuracy: the simple (OG − FG) × 131.25 approximation is calibrated around beer-strength worts. It drifts at the higher starting gravities common in wine, where the Balling-derived calculation is the more reliable choice.

Apparent attenuation for wine is almost always above 100 percent, which surprises people coming from beer. The formula is (OG minus FG) divided by (OG minus 1.000), and a dry wine finishes below 1.000 because the alcohol it contains is lighter than water, so the final gravity is below the starting point of the scale.

A dry white or red at 0.992 to 0.996 reads 104 to 110 percent. A wine at 1.000 to 1.005 is off-dry and still holds a few grams per litre of sugar. Anything that stops above 1.010 with a normal wine yeast is a stalled fermentation, usually from a nutrient shortfall, a cold cellar or a yeast that hit its alcohol tolerance on a high-Brix must. Use the number as a diagnostic rather than a target: healthy wine yeast ferments to dryness unless you stop it.