Gravity & ABV

Gravity is a measure of how much dissolved sugar is in your must or wine, relative to water. Water has a specific gravity (SG) of 1.000. A typical wine must sits between 1.080 and 1.110 before fermentation begins.

Original Gravity (OG)

OG is measured before yeast is pitched. A higher OG means more fermentable sugar and therefore more potential alcohol. Measure with a hydrometer or refractometer and record this as your starting point.

Final Gravity (FG)

FG is measured when fermentation is complete. A wine fully fermented to dryness typically ends at 0.995–1.000. Residual sugar raises FG above 1.000.

Calculating ABV

The standard simplified formula used by most home winemakers is:

For example: OG 1.095 − FG 0.998 = 0.097 × 131.25 = 12.7% ABV

Brix and Plato

Some winemakers use Brix (°Bx) instead of SG — 1 Brix ≈ 10g sugar per litre. A must at 1.090 SG is approximately 21.5 Brix. To convert: Brix × 0.004 + 1.000 ≈ SG.