ABV & Attenuation Calculator

Calculate Alcohol by Volume, Apparent Attenuation, and Real Extract Calories with Hall polynomial correction.

ABV & Attenuation Engine

Calculates Alcohol by Volume, yeast attenuation, and real extract calories.

Original Gravity (OG)

Hydrometer reading before yeast pitch

Final Gravity (FG)

Hydrometer reading at terminal gravity

Alcohol by Volume5.78%

Apparent Attenuation81.5%

Calories (12 oz)175 kcal

Mathematical Formula & Derivation

Hall Advanced High-Gravity ABV Equation

ABV = \frac{76.08 \times (OG - FG)}{1.775 - OG} \times \left(\frac{FG}{0.794}\right)

Standard homebrew formulas (OG - FG) * 131.25 underestimate alcohol in high-gravity worts. The Hall polynomial dynamically scales ethanol density against non-fermentable dextrin concentrations.

How to Use This Tool

1Record your Original Gravity (OG) before pitching yeast (e.g. 1.054).
2Record your Final Gravity (FG) once fermentation is completely stable over 3 consecutive days (e.g. 1.010).
3The engine automatically outputs true ABV %, apparent attenuation %, and calorie count per 12 oz bottle.

Tested Hardware Recommendation

Recommended Equipment for this Tool

Editorial Score: 93/100

NIST-Traceable Benchmark Specific Gravity Kit4.8 (2150 reviews)

Brewing America Triple Scale Hydrometer & Glass Test Jar Set

Cheap imported hydrometers are notoriously inaccurate, often off by 4-6 specific gravity points. Brewing America's hydrometers are hand-calibrated in the USA to NIST-traceable standards. Includes a crystal-clear heavy borosilicate glass test cylinder that won't cloud or scratch like cheap plastic cylinders, plus a microfiber cleaning cloth and storage case.

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Frequently Asked Questions

What is apparent attenuation versus real attenuation?

Apparent attenuation is what your hydrometer reads because ethanol has a lower specific gravity (0.789) than water, depressing the hydrometer bulb. Real attenuation accounts for alcohol density to measure actual sugar percentage converted by yeast.

Why does standard (OG - FG) * 131.25 fail on imperial stouts and double IPAs?

The 131.25 multiplier was designed for 1.040-1.055 session beers. As original gravity exceeds 1.070, ethanol production changes the specific volume of the solution, requiring the Hall polynomial to avoid understating alcohol by up to 0.8% ABV.