ABV Calculator (Alcohol by Volume)

Enter your Original Gravity (OG) and Final Gravity (FG) readings from your homebrew to calculate the Alcohol by Volume (ABV). Choose your gravity unit (SG or Plato) and equation type (Standard or Alternate) to get your ABV %, along with apparent attenuation and an estimated calorie count per 12 oz serving. Also try the Priming Sugar Calculator.

Gravity Unit *

Equation *

Standard: ABV = (OG – FG) × 131.25. Alternate uses a more complex formula for higher-gravity beers.

Gravity reading taken before fermentation begins.

Gravity reading taken after fermentation is complete.

Results

Alcohol by Volume (ABV)

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Apparent Attenuation

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Estimated Calories (per 12 oz)

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Alcohol by Weight (ABW)

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Frequently Asked Questions

What is ABV and why does it matter for homebrewing?

ABV stands for Alcohol by Volume — the percentage of the total beverage volume that is pure alcohol. For homebrewers, knowing your ABV helps you understand the strength of your batch, compare it to commercial styles, and ensure proper carbonation and packaging decisions.

What is Original Gravity (OG) and Final Gravity (FG)?

Original Gravity (OG) is a measure of the sugar content in your wort before fermentation begins. Final Gravity (FG) is measured after fermentation is complete. The difference between the two reflects how much sugar the yeast converted to alcohol and CO2, which is used to calculate ABV.

What's the difference between the Standard and Alternate ABV formulas?

The Standard formula (ABV = (OG – FG) × 131.25) is simple and widely used for typical beers. The Alternate formula (Miller/Mosher) is more accurate for higher-gravity beers above around 6% ABV, accounting for the density of alcohol affecting hydrometer readings. For most homebrew sessions, the standard formula is sufficient.

How do I convert Plato to Specific Gravity?

Plato (°P) is another scale for measuring sugar density, commonly used in commercial brewing. The approximate conversion is: SG ≈ 1 + (Plato / 250). For example, 14°P ≈ SG 1.056. This calculator handles Plato inputs directly so you don't need to convert manually.

What is Apparent Attenuation?

Apparent Attenuation is the percentage of sugars that the yeast has consumed during fermentation. It's calculated as: ((OG – FG) / (OG – 1)) × 100. A higher attenuation means a drier, less sweet beer. Most ale yeasts achieve 65–80% apparent attenuation.

How are calories in beer calculated?

Beer calories come from two main sources: alcohol and residual carbohydrates (unfermented sugars). This calculator estimates total calories per 12 oz serving by combining the caloric contribution of the alcohol content and the remaining fermentable sugars based on your FG reading.

What is Alcohol by Weight (ABW) and how does it differ from ABV?

ABW measures the mass of alcohol as a percentage of total beverage mass, while ABV measures volume. Because alcohol is less dense than water, ABW is always slightly lower than ABV. The conversion is: ABW ≈ ABV × 0.795. Some countries and labels use ABW instead of ABV.

Can I use a refractometer instead of a hydrometer for these readings?

Yes, but refractometer readings need to be corrected for the presence of alcohol when measuring FG. Alcohol affects the refractive index, causing the refractometer to read higher than the true gravity. Use a refractometer correction formula or calculator before entering the FG into this ABV calculator for accurate results.