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ABV Calculator

Estimate alcohol by volume, alternate ABV, apparent attenuation, and gravity points from original and final gravity readings.

  • alcohol by volume
  • original gravity
  • final gravity
  • apparent attenuation
  • homebrew abv

Specific gravity before fermentation, often written as OG.

Specific gravity after fermentation, often written as FG.

Optional serving size used for the beer calorie estimate.

Status: initial

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ABV beverage scale

Explore the abv calculator result visually while keeping this page's detailed guidance and examples.

ABV beverage scale
6.2%
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Use this result well

  1. 1Verify the calculator inputs.
  2. 2Compare the key result relationships.
  3. 3Review the page guidance before acting.

Hydrometer calibration, temperature, and fermentation completeness affect the estimate.

Calculator guide

Introduction

The ABV Calculator estimates alcohol by volume from original gravity and final gravity readings used in homebrewing and fermentation tracking.

What is ABV?

ABV means alcohol by volume. It estimates the percentage of a beverage's volume that is alcohol.

ABV formula

The common brewing estimate is ABV = (original gravity - final gravity) x 131.25. The calculator also shows apparent attenuation, real attenuation, alcohol by weight, Plato estimates, calories per serving, and an alternate ABV estimate.

Variable explanations

Understand what each input and result means before calculating.

Original gravity

Specific gravity before fermentation starts.

Final gravity

Specific gravity after fermentation is complete or stable.

Gravity drop

Original gravity minus final gravity.

ABV

Estimated alcohol by volume percentage.

ABW

Estimated alcohol by weight percentage.

Attenuation

Estimated percentage of gravity points fermented.

Serving size

Fluid ounces used for the calorie estimate.

Reviewed by the Calculator.org.in Editorial Team

Formula behavior, validation cases, explanatory examples, and cited sources are checked before publication. This review supports educational accuracy and is not a substitute for qualified professional advice.

Last reviewed: 2026-07-05

Review process

Formula guide

See the calculation logic, variable definitions, and practical meaning.

Standard ABV

ABV = (OG - FG) x 131.25

  • OG is original gravity.
  • FG is final gravity.

This is the widely used quick estimate for beer and homebrew ABV.

Alternate ABV

ABV = (76.08 x (OG - FG) / (1.775 - OG)) x (FG / 0.794)

  • OG and FG are specific gravity readings.

This alternate estimate can differ slightly, especially at higher alcohol levels.

Apparent attenuation

Apparent Attenuation = (OG - FG) / (OG - 1) x 100

  • Attenuation estimates how much gravity dropped during fermentation.

Use this to understand fermentation progress from gravity readings.

Alcohol by weight

ABW = ABV x 0.794 / FG

  • ABV is alcohol by volume.
  • FG is final gravity.

Alcohol by weight is useful when comparing older brewing references.

Real attenuation estimate

Real attenuation = (Original extract - real extract) / original extract x 100

  • Original extract and apparent final extract are estimated in Plato.

Real attenuation adjusts for alcohol's effect on final gravity, so it is lower than apparent attenuation.

Beer calorie estimate

Calories = alcohol calories + extract calories

  • Serving size controls the final calorie estimate.

This is a common homebrew estimate that combines alcohol and remaining extract calories.

Worked examples

Follow realistic inputs through the calculation step by step.

1

Worked example

Beer example

  1. 1OG is 1.055.
  2. 2FG is 1.015.
  3. 3Gravity drop is 0.040.
  4. 4Standard ABV is 5.25%.
2

Worked example

Lower gravity example

  1. 1OG is 1.040.
  2. 2FG is 1.010.
  3. 3Gravity drop is 0.030.
  4. 4Standard ABV is 3.94%.
3

Worked example

Higher gravity example

  1. 1OG is 1.080.
  2. 2FG is 1.018.
  3. 3Gravity drop is 0.062.
  4. 4Standard ABV is 8.14%.
4

Worked example

Calories per serving

  1. 1Enter OG and FG.
  2. 2Set serving size, such as 12 fl oz.
  3. 3Review the estimated calories per serving and batch profile.

Common mistakes

Avoid these common input and interpretation errors.

Using final gravity before fermentation is stable

If gravity is still dropping, the final ABV estimate can change.

Ignoring temperature correction

Hydrometer readings can need temperature correction depending on instrument calibration.

Using refractometer readings without correction

Refractometer readings after fermentation require alcohol correction.

Treating estimates as labeling compliance

Legal labeling, tax, or commercial reporting may require approved measurement methods.

Comparing apparent and real attenuation directly

Real attenuation adjusts for alcohol's effect on density, so it is normally lower than apparent attenuation.

Frequently asked questions

Quick answers to the questions users ask most often.

What does this ABV Calculator calculate?
It estimates standard ABV, alternate ABV, apparent attenuation, and gravity points dropped.
What is the standard ABV formula?
ABV equals original gravity minus final gravity, multiplied by 131.25.
What is original gravity?
Original gravity is the specific gravity reading before fermentation starts.
What is final gravity?
Final gravity is the specific gravity reading after fermentation is complete or stable.
What is apparent attenuation?
Apparent attenuation estimates the percentage of gravity points consumed during fermentation.
Why does the calculator show alternate ABV?
The alternate formula can produce a slightly different estimate, especially for higher-gravity beverages.
What is alcohol by weight?
Alcohol by weight, or ABW, estimates alcohol as a percentage of weight instead of volume.
What is real attenuation?
Real attenuation estimates fermentation progress after adjusting for alcohol's effect on the final gravity reading.
Does this calculator estimate calories?
Yes. It estimates calories per serving from alcohol by weight, real extract, final gravity, and serving size.
Can final gravity be higher than original gravity?
Not for a normal fermentation ABV estimate. Final gravity must be lower than original gravity.
Does this work for beer?
Yes. The standard OG and FG formula is commonly used for beer and homebrewing estimates.
Does this work for wine or cider?
It can provide a rough estimate from gravity readings, but beverage-specific methods may differ.
Does this correct refractometer readings?
No. Refractometer readings after fermentation need separate alcohol correction.
Does this correct for hydrometer temperature?
No. Enter temperature-corrected readings if your hydrometer requires correction.
Can I use this for commercial labeling?
No. Commercial labeling and tax reporting may require approved lab methods and jurisdiction-specific rules.
Why is 131.25 used?
It is a common empirical factor used to estimate ABV from the gravity difference.
What are gravity points?
Gravity points are the decimal gravity difference multiplied by 1,000.
Is this legal advice?
No. It is an estimate-only brewing math calculator.

References

Sources used to support the calculator guidance.

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Version history

A transparent record of calculator content updates.

Updated 2026-07-05
  • 1.0.0 · 2026-07-05

    Initial ABV calculator release.