ABV Calculator

Estimate the alcohol content of home-brewed beer or wine.

How the Math Works

The ABV Calculator uses a fundamental relationship between original and final gravity readings to determine alcohol content. When fermentable sugars are converted to alcohol by yeast, the specific gravity of the liquid decreases. The formula ABV ≈ (OG - FG) × 131.25 captures this change: subtract the final gravity from the original gravity to find the gravity points lost during fermentation, then multiply by 131.25 to convert this difference into approximate alcohol by volume percentage. This constant derives from the density relationship between sugar conversion and alcohol production, making it a reliable estimation method for homebrewers and professionals alike.

Practical Applications

To use this calculator, first measure your original gravity (OG) before fermentation begins using a hydrometer or refractometer, recording the specific gravity reading. After fermentation completes, take a final gravity (FG) measurement once the activity has slowed significantly. Enter these values into the calculator: for example, an OG of 1.050 and FG of 1.010 yields (1.050 - 1.010) × 131.25 = 5.25% ABV. This calculation helps you verify if your beer or wine is reaching expected strength levels and provides essential data for recipe development, scaling batches, and ensuring consistent results across brewing sessions.

Day-to-Day Use

Knowing your alcohol content enhances your brewing experience in practical ways: it helps you plan appropriate serving sizes, estimate alcohol effects for social gatherings, and ensure your homemade beverages fall within legal and personal safety guidelines. Whether you're hosting a party and need to calculate how many servings your batch will provide, or tracking alcohol content for dietary reasons, this tool gives you precise information. It also enables you to compare different recipes, perfect your brewing techniques, and share accurate details with fellow enthusiasts when discussing or trading homemade brews.

Worked example

OG 1.050, FG 1.010 → 5.25% ABV.

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