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ABV Calculator

Calculate the Alcohol By Volume (ABV) of beer, wine, or cider from original and final gravity readings.

Reviewed by Christopher FloiedPublished Updated

This free online abv calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.

Specific gravity before fermentation

Specific gravity after fermentation

Results

ABV

5.25%

Apparent Attenuation

80%

How to Use This Calculator

1

Enter your input values

Fill in all required input fields for the ABV Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.

2

Review your inputs

Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.

3

Read the results

The ABV Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.

4

Explore parameter sensitivity

Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.

Formula Reference

ABV Calculator Formula

See calculator inputs for the governing equation

Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.

When to Use This Calculator

  • •Use the ABV Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
  • •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
  • •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
  • •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.

About This Calculator

The ABV Calculator is a free, browser-based calculation tool for engineers, students, and technical professionals. Calculate the Alcohol By Volume (ABV) of beer, wine, or cider from original and final gravity readings. It implements standard formulas and supports both metric (SI) and imperial unit systems with automatic unit conversion. All calculations are performed instantly in your browser with no data sent to a server. Use this calculator as a quick reference and sanity-check tool during design, analysis, and learning. Always verify results against primary engineering references and applicable standards for any safety-critical application.

About ABV Calculator

Alcohol By Volume (ABV) is the standard measure of alcohol content in fermented beverages. For homebrewers and winemakers, ABV is calculated by measuring the specific gravity of the liquid before fermentation (Original Gravity, OG) and after fermentation (Final Gravity, FG). The difference between these two readings indicates how much sugar was converted to alcohol by the yeast. This calculator uses the widely accepted formula ABV = (OG - FG) x 131.25, which provides accurate results for most homebrew applications. It also calculates apparent attenuation, which tells you what percentage of the available sugars were fermented.

The Math Behind It

Fermentation is the metabolic process by which yeast converts sugars (primarily glucose and maltose) into ethanol and carbon dioxide. The specific gravity of a liquid measures its density relative to water (which has a gravity of 1.000). Dissolved sugars increase the gravity above 1.000, while alcohol (which is less dense than water) decreases it. By measuring gravity before and after fermentation, you can calculate how much sugar was converted. The constant 131.25 in the ABV formula is an empirically derived approximation. A more precise formula used by some brewers is ABV = (76.08 x (OG - FG) / (1.775 - OG)) x (FG / 0.794), which accounts for the non-linear relationship between gravity and sugar content at higher gravities. For beers under 8% ABV, both formulas yield nearly identical results. Apparent attenuation measures the percentage of gravity points consumed: (OG - FG) / (OG - 1) x 100. Most ale yeasts attenuate 72 to 78 percent, while lager yeasts may reach 80 to 85 percent. Higher attenuation produces a drier, thinner beer, while lower attenuation leaves more residual sweetness and body.

Formula Reference

ABV Formula

ABV = (OG - FG) x 131.25

Variables: OG = Original Gravity, FG = Final Gravity (hydrometer readings).

Apparent Attenuation

AA = (OG - FG) / (OG - 1) x 100%

Variables: Measures what percentage of sugars were consumed.

Worked Examples

Example 1: Standard pale ale

OG = 1.050, FG = 1.010

Step 1:ABV = (1.050 - 1.010) x 131.25 = 0.040 x 131.25 = 5.25%
Step 2:Attenuation = (0.040 / 0.050) x 100 = 80%

The beer has an ABV of 5.25% with 80% apparent attenuation.

Common Mistakes & Tips

  • !Forgetting to take the original gravity reading before adding yeast.
  • !Not correcting hydrometer readings for temperature (most hydrometers are calibrated at 60F).
  • !Using the formula on high-gravity beers (above 1.090) where it becomes less accurate.
  • !Confusing ABV (alcohol by volume) with ABW (alcohol by weight), which is about 20% lower.

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Frequently Asked Questions

What is original gravity?

Original Gravity (OG) is the specific gravity of the wort or must before fermentation begins. It indicates the amount of dissolved sugars available for the yeast to convert to alcohol. A higher OG means more potential alcohol.

How accurate is this formula?

The (OG - FG) x 131.25 formula is accurate within +/- 0.1% ABV for beers and wines up to about 8% ABV. For stronger beverages, use the more complex alternative formula for improved accuracy.