How to measure the alcohol in homemade wine
Wine yeast turns sugar into alcohol, and sugar is denser than alcohol, so the must gets lighter as it ferments. A hydrometer measures that drop in density (specific gravity), and the size of the drop tells you how much alcohol was made.
- Before you pitch the yeast, take a sample of the must and record the starting gravity (SG). Most table wines start between 1.080 and 1.100.
- When fermentation is finished, and the gravity has stayed the same for three days in a row, take a second reading. This is the final gravity.
- Enter both readings above to get the alcohol by volume (ABV).
If your sample isn't at your hydrometer's calibration temperature, correct it first with the hydrometer temperature correction calculator. If you use a refractometer, the refractometer calculator corrects for the alcohol that skews Brix readings once fermentation starts.
Which equation should I use for wine?
The familiar ABV = (OG − FG) × 131.25 formula was developed for beer. It works well up to about 7% ABV, but it increasingly underestimates stronger drinks. The alternate equation (Hall, Zymurgy 1995) follows measured alcohol more closely at wine strength, so this calculator uses it by default. At 1.100 to 0.996, for example, the standard formula gives 13.7% and the alternate gives about 14.4%.
Reading your result
- Final gravity below 0.998: dry wine. Alcohol is lighter than water, so a fully fermented wine can read below 1.000.
- 1.000 to 1.010: off-dry, with noticeable residual sugar.
- Above 1.010: sweet or dessert style. If you expected a dry wine, the fermentation may have stalled.
To reach a specific strength, use the chaptalization calculator to work out how much sugar to add before fermentation. Making fruit or honey wine? See the mead calculator.
Method and sources
- Alternate equation: ABV = 76.08 × (OG − FG) / (1.775 − OG) × FG / 0.794. This is Michael Hall's published equation for alcohol by weight, converted to alcohol by volume by multiplying by FG / 0.794 (0.794 is the specific gravity of pure ethanol).
- Standard equation: ABV = (OG − FG) × 131.25. This is the straight-line shortcut most homebrew software uses. The two equations agree closely for normal-strength beer and drift apart as the starting gravity rises.
- Brix and Plato: converted from gravity with a standard brewing polynomial. We checked it against the reference polynomial below, and the two agree within 0.1 °Bx between 1.000 and 1.140.
Every gravity-based ABV is an estimate. A lab measures alcohol directly, and its result can differ slightly from any hydrometer formula.
Sources
Frequently asked questions
How do you calculate the alcohol content of homemade wine?
Take a hydrometer reading before fermentation (original gravity) and after (final gravity). ABV is roughly (OG - FG) x 131.25, but for wine the alternate equation is more accurate because the standard one reads low above about 7% ABV.
What should the final gravity of wine be?
A dry wine usually finishes between 0.990 and 0.998. Off-dry wines finish around 1.000 to 1.010, and sweet or dessert wines finish above 1.010.
What starting gravity do I need for 12% wine?
About 1.085 to 1.090 if the wine ferments dry to around 0.996. Use the chaptalization calculator to work out how much sugar to add to reach it.