ABV Calculator (Alcohol by Volume)

How to use this alcohol by volume calculator

What this calculator does

This calculator estimates the alcohol content of fermented beer from two hydrometer readings: original specific gravity before fermentation and final specific gravity after fermentation. It converts those readings to degrees Plato, applies an empirical brewing model for alcohol by weight and alcohol by volume, and reports attenuation, proof, and the volume of pure ethanol in the entered serving or batch. It is useful for recipe development and production records, but it is not a laboratory assay, a legal label approval, or a blood-alcohol calculator. For an accessible overview of how ABV is measured in beverages, see the NIST explanation of alcohol measurement.

When to use it

Use it when checking whether a homebrew reached its expected strength, comparing attenuation across yeast strains or fermentation conditions, estimating the alcohol in a bottle or keg, or preparing a preliminary production worksheet before a more formal laboratory test. It also helps translate one brewing result into ABW, US proof, UK proof, and extract values without manually repeating several formulas.

How to calculate

1. The calculator opens with a complete demonstration: OG 1.060, FG 1.015, and 330 mL. Results and a validated Excel workbook are available immediately.
2. Replace Original specific gravity (OG) with the calibrated hydrometer reading taken before fermentation.
3. Replace Final specific gravity (FG) with the stable reading taken after fermentation. It must not exceed OG for this standard fermentation model.
4. Enter Total beverage volume and choose mL, L, fl oz, or US gal. Changing the unit converts the current amount rather than merely relabeling it.
5. Read the live ABV and supporting results, then select Download Excel to export the current typed inputs and calculated values. Reset clears the demonstration data and may disable export until a complete valid state is entered again.

Input guide

Original specific gravity (OG) is required, unitless, and accepts a plain decimal from 1.000 to 1.200 using a period as the decimal separator; 1.060 is a realistic example. A higher OG generally increases potential alcohol when FG is unchanged. Do not enter 60, 1060, scientific notation, a decimal comma, or a Plato value in this field. Final specific gravity (FG) is also required and uses the same format and range; 1.015 is the startup example. Lower FG usually raises ABV and attenuation. A final reading above OG is rejected because it does not represent ordinary alcoholic fermentation under this model. Total beverage volume is required, must be a finite positive number, and accepts a period decimal with no grouping separators; 330 mL is the example. It changes only the pure alcohol volume, not ABV. The Total volume unit control converts the current value among milliliters, liters, US fluid ounces, and US gallons; selecting a different unit should preserve the same physical quantity.

Output guide

Alcohol by volume (ABV) is the estimated ethanol volume percentage and is the primary result. Alcohol by weight (ABW) expresses ethanol as a percentage of beverage mass. US proof equals twice ABV; UK proof uses the historical 57.15% ABV = 100 proof relationship. Pure alcohol volume is the entered total volume multiplied by ABV and is displayed in the selected unit. In the detail table, Original extract (OE) and Apparent extract (AE) are specific-gravity conversions to degrees Plato, while Real extract (RE) adjusts apparent extract for alcohol's effect on density. Apparent degree of fermentation (ADF) and Real degree of fermentation (RDF) estimate attenuation. Zero ABV is valid only when OG and FG are equal; unusually high values should prompt a check of hydrometer calibration, temperature correction, and input format.

Worked example

With OG 1.060 and FG 1.015, the gravity-to-Plato conversion gives OE 14.7414 °P and AE 3.8263 °P. The empirical model estimates ABW at 4.6349% and ABV at 5.9497%, displayed as 5.95%. Apparent attenuation is 74.04%, and a 330 mL bottle contains 330 × 0.0594966 = 19.63 mL of pure ethanol. The same values appear in the first-open results and workbook.