Calculator.org.in
Calculator

ABV Calculator

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

Specific gravity before fermentation, often written as OG.

Specific gravity after fermentation, often written as FG.

Status: initial

Results

Awaiting calculation

Brewing math

Introduction

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

The common brewing estimate is ABV = (original gravity - final gravity) x 131.25. The calculator also shows apparent attenuation and an alternate ABV estimate.

Formula and method guide

Standard ABV

ABV = (OG - FG) x 131.25

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)

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

Apparent attenuation

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

Use this to understand fermentation progress from gravity readings.

Variables

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.

Attenuation

Estimated percentage of gravity points fermented.

FAQs

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.
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

Related calculators