What is Alcohol by Volume (ABV)?
ABV (Alcohol by Volume) is the standard worldwide measure of how much alcohol (ethanol) is contained in a given volume of an alcoholic beverage. It is expressed as a volume percent: the number of milliliters of pure ethanol present in 100 mL of solution at 20 °C (68 °F). This ABV calculator lets you estimate the alcohol content of your homebrew beer, wine, or any fermented drink using its original and final specific gravity.
Calculating ABV from Specific Gravity
When yeast ferments sugars, the density (specific gravity) of your liquid drops. By measuring the gravity before fermentation (Original Gravity, OG) and after (Final Gravity, FG), you can precisely calculate how much alcohol was produced. The formula used here is the peer-reviewed Cutaia–Reid–Speers formula (2009), published in the Journal of the Institute of Brewing:
- Convert specific gravity to Plato degrees: P = 135.997 × SG³ − 630.272 × SG² + 1111.14 × SG − 616.868
- Calculate Alcohol by Weight (ABW): ABW = (0.372 + 0.00357 × OE) × (OE − AE)
- Calculate ABV: ABV = ABW × (1.308×10⁻⁵ + 3.868×10⁻³ × AE + … + 1) / 0.7907
Difference between ABV, ABW and Proof
- ABV — Alcohol by Volume: milliliters of ethanol per 100 mL of drink.
- ABW — Alcohol by Weight: grams of ethanol per 100 g of drink. ABW is always lower than ABV because ethanol is lighter than water.
- US Proof — exactly twice the ABV. A 50% ABV spirit is 100 proof.
- UK Proof — defined so that 100-proof spirit has 57.15% ABV. Therefore UK proof = ABV × 100 / 57.15.
Using the ABV Calculator — Example
Suppose you brewed a batch of ale. Your hydrometer read 1.060 before fermentation (OG) and 1.015 after (FG). Enter those values and the calculator instantly shows:
- ABV ≈ 5.95%
- ABW ≈ 4.70%
- US Proof ≈ 11.9
- OE ≈ 14.74 °P, AE ≈ 3.83 °P
If you enter a volume (e.g. 330 ml for a standard bottle), the calculator also shows the pure alcohol volume: 330 × 5.95% ≈ 19.6 ml.
What is Alcohol?
Alcohol (ethanol, C₂H₅OH) is an organic compound produced when yeast ferments sugars. Common alcoholic beverages and their typical ABV ranges:
- Beer: 2–6%
- Cider: 4–8%
- Wine: 8–20%
- Spirits (vodka, rum, whiskey, gin): 40–50%
- Liqueurs: 15–60%
Alcohol Facts
- Ethanol is classified as a sedative-hypnotic drug at high doses.
- Blood Alcohol Concentration (BAC) determines impairment — not the type of drink.
- Fermented drinks contain 2–20% ABV; distilled spirits typically 40–50%+.
- Proof was historically tested by soaking gunpowder in spirit: if it still ignited, the spirit was "above proof".
Frequently Asked Questions
- Can I use this for wine or cider?
- Yes. The Cutaia–Reid–Speers formula works for any fermented beverage — beer, wine, cider, mead, or kombucha.
- What is Plato degrees?
- Plato (°P) measures the concentration of dissolved sugars in wort. It is mathematically related to specific gravity via a cubic polynomial.
- Why is ABW lower than ABV?
- Because ethanol (density ≈ 0.789 g/ml) is lighter than water. The same volume of ethanol weighs less, so the weight percentage is lower than the volume percentage.
- Is this formula accurate?
- The Cutaia–Reid–Speers formula is one of the most accurate empirical models available, derived from pilot-plant and commercial brewery data. All ABV formulas are approximations; lab analysis is the only method for legal labelling.