Wine ABV Calculator

How it is calculated

The tool converts each Brix reading to specific gravity (SG) with a cubic-style formula, then turns the SG drop into alcohol: SG = 1 + Brix ÷ (258.6 − (Brix ÷ 258.2) × 227.1) and ABV = (SG_start − SG_end) × 131.25. Brix is degrees of dissolved sugar per 100 g of liquid, and the result is percent alcohol by volume with two decimals. The estimate therefore depends on how far the sugar reading fell, not on a flat factor such as Brix × 0.55. The starting value must be above 0 and at most 100, and the final value must be between 0 and the starting value (0 is allowed for a bone-dry wine); anything else gives no result. Fermentation efficiency, residual sugar and the effect of alcohol on a refractometer reading are not corrected for.

Common mistakes

• Using a refractometer reading after fermentation without correcting it. Alcohol bends light too, so a refractometer's final Brix reads higher than the real sugar level and the ABV comes out too low; use a hydrometer reading, or a corrected one, for the final value.
• Entering specific gravity instead of Brix. Values like 1.095 and 1.005 are gravities, not Brix; typed in, they are accepted and give a meaningless 0.05 %, whereas a typical must reads around 20 to 26 Brix.
• Typing a negative final reading when an instrument shows a dry wine below 0. Negatives are rejected, so enter 0 for a bone-dry wine.
• Swapping start and final. If the final Brix is higher than the starting one, there is no result.
• Treating the figure as exact. It assumes the lost sugar became alcohol at a fixed ratio, so it is an estimate and can be a little off from a lab measurement.