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Homebrew ABV Calculator

Compare separate empirical ABV estimates from measured original and final gravity, with apparent attenuation and theoretical package capacity.

Use this result well

Inputs that matter
Measured original and final gravity, measured batch volume, and nominal package volume
Output to expect
Separate common-linear and alternate empirical ABV estimates, apparent attenuation, batch volume, and theoretical no-loss package capacity
How it works
Apply each gravity equation independently; never average the estimates, and divide measured batch fluid ounces by package volume only as theoretical capacity
  • Record instrument type, calibration, sample temperature, and any refractometer alcohol correction; confirm final-gravity stability separately.
  • The output is not laboratory measurement, legal labeling, packaging yield, calorie content, or a basis for driving or consumption decisions.

Choose your path

Built around the job you need to finish

Compare reproducible gravity-based ABV estimates without blending methods or turning theoretical batch volume into consumption, calorie, legal-label, or packaging-yield claims.

Home brewer with hydrometer readings

Estimate ABV from a stable OG and FG.

Enter measured gravity readings and compare two separately labeled empirical equations.

Records the method and never treats an average of equations as a standard.

Cider or mead maker

Handle a dry final gravity below 1.000.

Enter valid FG below OG and inspect attenuation context.

Gets valid arithmetic without ale-style flavor or fermentation diagnosis.

Packaging planner

Estimate capacity before losses.

Enter measured batch and nominal package volumes.

Reads a decimal theoretical capacity and plans real transfer/headspace/losses separately.

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Projects using Homebrew ABV Calculator

This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.

Homebrew Batch Decision Record

Coordinate one lawful personal-use beer batch through people, recipe and product evidence, hot-liquid and pressure controls, bounded gravity/bitterness/priming scenarios, measured fermentation, packaging and named acceptance.

6 steps3 toolsStart project

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Reference & details

How it works

Standard gravity formula

ABV is estimated from the drop between original gravity and final gravity. This is the common homebrew formula for beer, cider, and mead planning.

ABV = (OG - FG) x 131.25

Attenuation and capacity

Apparent attenuation compares gravity drop with original gravity above 1.000. Batch gallons divided by package volume gives decimal theoretical capacity before transfer, trub, sampling, priming, headspace, or packaging losses.

Estimate boundaries

The common linear and alternate gravity equations remain separate; the calculator does not average them. Instrument calibration, temperature, refractometer alcohol correction, laboratory accuracy, legal labeling, calories, and consumption decisions remain outside the result.

Updated: August 2026

Example Scenarios

Enter OG and FG after stable readings to estimate ABV before packaging.

Calculate the gravity ratio, then compare it with your documented recipe, process, instrument method, and expected fermentation separately.

Divide measured batch volume by nominal package volume, then subtract real transfer, trub, sampling, priming, headspace, and packaging losses outside the tool.

Common Mistakes to Avoid

Using refractometer FG without correction

Alcohol changes refractometer readings. Use a correction calculator or a hydrometer for final gravity.

Packaging before gravity is stable

Take stable readings over multiple days before bottling to reduce overcarbonation risk.

FAQ

Use original gravity minus final gravity, then multiply by 131.25. For example, 1.052 to 1.012 is about 5.25% ABV.

Yes. The gravity formula works as an estimate for beer, cider, mead, wine, and similar fermentations.

No. It is gravity arithmetic. Recipe composition, organism, temperature, oxygen, nutrients, instrument error, contamination, and process history require separate evaluation.

They are different empirical equations and can diverge. The tool keeps them separately labeled rather than averaging them into a third method.

The arithmetic is reproducible for the entered readings, but measurement quality and empirical-formula limits control real accuracy. Use calibrated instruments or a qualified laboratory for consequential or legal results.

About Homebrew ABV Calculator

Enter measured original and final gravity to compare two separately labeled empirical ABV estimates. Batch and package volumes show only theoretical no-loss capacity, not finished yield.