Free tools for winemakers
ABV calculator
Alcohol from the starting and final readings
Alcohol (ABV)
Type the starting and the final reading.
Final reading: hydrometer only. Alcohol makes a refractometer read high, so a refractometer final reading gives too little alcohol. The starting reading can come from either.
An estimate. Readings give a close estimate, not a lab figure. For the label, have the alcohol measured.
How do we calculate this?
The exact formulas used in this tab:
What this calculator does
Works out how much alcohol a fermentation made, from the sugar reading taken before it started and the reading at the end.
- Each reading can be in its own scale: Brix, specific gravity (SG), Baumé, Oechsle or KMW.
- A final reading below 1.000 SG, as in a dry wine, is fine.
- The answer is (OG − FG) × 131.25 with both readings as SG: a close estimate, not a lab figure.
The formula
OG, FG = starting and final readings, as SGABV (% vol) = (OG − FG) × 131.25Check: 24 °Brix ≈ 240 g/L fermentable sugar (about 90% of the dissolved solids) × 0.47 g ethanol per g ÷ 0.789 g/mL ≈ 14.3 % vol
Worked example
Readings in SG
- Start: 1.090 SG
- End, dry: 0.995 SG
- How far the reading dropped 1.090 − 0.995 = 0.095
- Alcohol 0.095 × 131.25 = 12.5 % vol
The fermentation made about 12.5 % vol alcohol
Readings in Brix
- Start: 22 °Bx
- End: −1.5 °Bx
- Start reading as SG 22 °Bx = 1.0920 SG
- End reading as SG −1.5 °Bx = 0.9942 SG
- Alcohol (1.0920 − 0.9942) × 131.25 = 12.8 % vol
The fermentation made about 12.8 % vol alcohol
Questions
Why must the final reading come from a hydrometer?
A refractometer measures how the liquid bends light, and alcohol bends it too. So once fermentation has started, a refractometer reads high. A high final reading makes the drop look smaller and the alcohol come out too low. A hydrometer floats in the wine and reads its real density. The starting reading, taken before fermentation, can come from either.
My wine reads below 1.000. Is that a mistake?
No. Alcohol is lighter than water, so a dry wine often reads about 0.990–0.998 SG, or a negative Brix. Type the reading as it is; the formula uses it directly. The calculator only refuses a final reading below 0.960 SG, which no wine reaches.
Why not the “high-gravity” formula?
That formula comes from beer brewing, and on wine musts it reads about one percentage point high. The formula used here matches the sugar it stands for. A 24 °Brix must holds about 240 g/L of sugar that can ferment. At about 0.47 g of alcohol per gram of sugar, that is about 14.3 % vol. The formula gives 14.2 % vol for that must fermented dry to 0.993 SG. Either way it is an estimate; for the label, have the alcohol measured in a lab.
High-gravity formula: M. L. Hall, Zymurgy, 1995.
Do I need to correct the readings for temperature?
Yes, if the wine was much warmer or colder than the temperature your hydrometer is calibrated for, often 20 °C. Correct each reading first, then type the corrected figures here.