Which ABV formula should I use?

Use the Advanced (Terrill) method for most homebrew scenarios as it compensates for non-linearity at higher gravities. The Standard method is simpler and close enough for low to moderate OG beers.

Do I need hydrometer temperature correction?

Correct if your sample temperature differs from the hydrometer calibration temperature (often 20°C or 60°F). Significant differences can bias OG/FG and final ABV.

Can FG be higher than OG?

No. If FG exceeds OG, re-check measurements or temperature corrections. The calculator requires FG to be less than OG.

What is Apparent vs Real Extract?

Apparent Extract uses hydrometer readings uncorrected for alcohol's lower density; Real Extract adjusts for alcohol presence to better reflect residual sugars.

How accurate is this calculator?

It uses industry-standard relationships (ASBC/Plato) and the Terrill correlation. Accuracy depends on precise gravity readings and appropriate temperature correction.

Does this work with refractometers?

This version is optimized for hydrometer readings (Specific Gravity). For refractometers, apply wort correction and alcohol corrections or use a dedicated refractometer calculator.

homebrew abv calculator

A precise, accessibility-first tool for homebrewers to compute Alcohol by Volume (ABV) and related metrics from Original Gravity (OG) and Final Gravity (FG). Choose between Standard or Advanced methods, apply hydrometer temperature correction, and get Plato-based analytics instantly.

Calculator

Standard Advanced (Terrill)

Standard: ABV = (OG − FG) × 131.25. Advanced: Terrill correlation for improved accuracy.

Original Gravity (OG) *

Final Gravity (FG) *

Apply hydrometer temperature correction

Corrects SG readings when measured at temperatures different from your hydrometer’s calibration.

Results

Alcohol by Volume (ABV)

0.00%

Alcohol by Weight (ABW)

0.00%

Original Extract

0.00 °P

Final Extract (Apparent)

0.00 °P

Real Extract

0.00 °P

Apparent Attenuation

0.0%

Results update automatically as you type. Values are rounded for readability.

Data Source and Methodology

Authoritative Data Source: American Society of Brewing Chemists (ASBC), Methods of Analysis. Wort-12: Extract—Specific Gravity and Plato (2014), and Beer-4/Beer-6: Alcohol in Beer (various editions). Official resource: asbcnet.org — Methods of Analysis. Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

For enhanced ABV accuracy we implement the widely used Terrill correlation alongside the standard linear factor method. Hydrometer temperature correction follows the polynomial water density compensation commonly used in brewing software.

The Formula Explained

LaTeX notation is shown; variables are defined in the Glossary.

1) Standard ABV

ABV_{\%} = (OG - FG) \times 131.25

2) Advanced ABV (Terrill)

ABV_{\%} = \frac{76.08 \times (OG - FG)}{1.775 - OG} \times \frac{FG}{0.794}

3) Plato (°P) from Specific Gravity

P = -616.868 + 1111.14\,SG - 630.272\,SG^{2} + 135.997\,SG^{3}

4) Real Extract (Balling)

RE = 0.1808 \times P_{OG} + 0.8192 \times P_{FG}

5) Apparent Attenuation

AA_{\%} = \frac{P_{OG} - P_{FG}}{P_{OG}} \times 100

6) Alcohol by Weight

ABW_{\%} = \frac{0.79336 \times ABV_{\%}}{FG}

7) Hydrometer Temperature Correction

SG_{corr} = SG_{obs} \times \frac{CF(T_{sample})}{CF(T_{cal})} CF(T) = 1.00130346 - 1.34722124\times10^{-4}T + 2.04052596\times10^{-6}T^{2} - 2.32820948\times10^{-9}T^{3}

Glossary of Variables

Original Gravity (OG): Specific gravity of wort before fermentation (e.g., 1.050).
Final Gravity (FG): Specific gravity after fermentation; typically lower than OG (e.g., 1.010).
ABV (%): Alcohol by Volume; primary strength measure for beer.
ABW (%): Alcohol by Weight; ABV scaled by beer density.
Plato (°P): Percentage by weight of dissolved extract (sugars) in wort/beer.
Real Extract (RE): Extract adjusted for alcohol presence, approximating residual sugars.
Apparent Attenuation (AA%): Degree to which fermentable extract appears to have been consumed.
Temperature Correction: Adjustment to SG readings when sample temperature differs from hydrometer calibration.

How It Works: A Step-by-Step Example

Inputs: OG = 1.050, FG = 1.012, 20°C sample, 20°C calibration (no temperature bias).
Convert to Plato: P_{OG} \approx 12.39\,°P,\; P_{FG} \approx 3.07\,°P
Standard ABV: ABV = (1.050 - 1.012)\times 131.25 \approx 4.99\%
Advanced (Terrill): ABV \approx \frac{76.08\times 0.038}{1.775 - 1.050}\times \frac{1.012}{0.794} \approx 5.08\%
ABW from ABV and FG: ABW \approx \frac{0.79336\times 5.08}{1.012} \approx 3.98\%
Real Extract: RE = 0.1808 \times 12.39 + 0.8192 \times 3.07 \approx 4.71\,°P
Apparent Attenuation: AA = \frac{12.39 - 3.07}{12.39}\times 100 \approx 75.2\%

Frequently Asked Questions (FAQ)

Which ABV method should I choose?

The Advanced (Terrill) method is recommended for improved accuracy, especially for higher gravity beers. The Standard method is sufficient for low to moderate OG beers.

How far can the sample temperature be from calibration before I must correct?

Any difference can bias results, but corrections become important beyond ~5–6°C (10°F). Use the correction option for best accuracy.

Why do Plato values matter?

Plato expresses extract as mass percentage and underpins professional brewing calculations, enabling Real Extract and attenuation metrics.

Is ABW just ABV times a constant?

ABW is derived from ABV and the beer’s density (FG). We use ABW = 0.79336 × ABV / FG.

My FG equals OG. What does it mean?

Fermentation likely did not start or the readings are off. Recheck calibration, temperature, and measurement technique.

Can this calculator handle refractometer readings?

This tool targets hydrometer SG. For refractometers, a wort correction factor and alcohol correction are required. Use a refractometer-specific calculator.

Are the formulas peer-reviewed?

The Plato relationships trace back to Balling/Plato and are standardized in ASBC methods. The Terrill correlation is a widely accepted empirical improvement used by many brewing tools.

Strumento sviluppato da Ugo Candido,. Contenuti verificati da,.

Ultima revisione per l'accuratezza in data: September 12, 2025.