Alcohol by Volume Calculator
Calculate the alcohol by volume (ABV) of your homebrew beer, wine, or cider using original and final gravity readings. Also shows apparent attenuation, calories, and standard drinks. See also our Alcohol Dilution Calculator and Cooking Converter.
How to Calculate Alcohol by Volume
Alcohol by Volume (ABV) measures the percentage of alcohol in a beverage. For homebrewers, ABV is calculated by measuring the gravity of the wort or must before fermentation (Original Gravity or OG) and after fermentation is complete (Final Gravity or FG). The difference between these two readings tells you how much sugar was converted to alcohol by the yeast.
To use this calculator, take a hydrometer or refractometer reading before pitching yeast (this is your OG). Once fermentation is complete (gravity readings are stable for 2-3 consecutive days), take another reading (this is your FG). Enter both values and the calculator will determine your ABV, apparent attenuation, estimated calories, and standard drink equivalents.
You can input gravity in three formats: Specific Gravity (SG), which is the most common for homebrewers (water = 1.000); Brix, which measures sugar content as a percentage by weight and is popular with winemakers; or Plato, which is similar to Brix and commonly used in professional brewing. The calculator automatically converts between these units.
ABV Formula
ABV% = (OG - FG) × 131.25
Apparent Attenuation% = ((OG - FG) / (OG - 1)) × 100
Calories (per 12oz) = Alcohol Calories + Residual Carb Calories
Standard Drinks = Volume(ml) × ABV × 0.789 / 14g
The standard ABV formula (OG - FG) × 131.25 is a simplified version that works well for beers under 6% ABV. For higher-gravity beers and wines, a more accurate formula accounts for the non-linear relationship between gravity and alcohol production. The constant 131.25 is derived from the molecular weight ratio of ethanol to CO2 produced during fermentation, adjusted for the density change.
Apparent attenuation tells you what percentage of the available sugars were fermented. Most beer yeasts achieve 70-80% apparent attenuation. Higher attenuation means a drier, less sweet beer. Belgian yeasts and champagne yeasts can achieve 85-95% attenuation. If your attenuation is unusually low (below 65%), fermentation may have stalled.
Example Calculation
Let us calculate the ABV for a typical pale ale with OG 1.050 and FG 1.010:
Step 1: ABV = (1.050 - 1.010) × 131.25 = 0.040 × 131.25 = 5.25%
Step 2: Attenuation = ((1.050 - 1.010) / (1.050 - 1.000)) × 100 = (0.040 / 0.050) × 100 = 80%
Step 3: Calories ≈ 5.25 × 1.8 × 3.55 × 0.789 + (0.010 × 1000 × 3.55 × 3.8) ≈ 26.5 + 134.9 ≈ 161 cal per 12oz
Step 4: Standard Drinks = (355 × 0.0525 × 0.789) / 14 = 1.05 standard drinks per 12oz
Result: This pale ale is 5.25% ABV with 80% apparent attenuation, approximately 161 calories per 12oz serving, and just over 1 standard drink.
Common Beer Style ABV Reference Table
| Beer Style | Typical OG | Typical FG | ABV Range | Calories/12oz |
|---|---|---|---|---|
| Light Lager | 1.028-1.040 | 0.998-1.008 | 3.2-4.2% | 95-120 |
| Pale Ale | 1.044-1.060 | 1.008-1.014 | 4.5-6.2% | 150-180 |
| IPA | 1.056-1.075 | 1.010-1.018 | 5.5-7.5% | 180-230 |
| Stout | 1.036-1.076 | 1.007-1.018 | 4.0-7.0% | 150-210 |
| Belgian Tripel | 1.075-1.085 | 1.008-1.014 | 7.5-9.5% | 220-280 |
| Barleywine | 1.085-1.120 | 1.016-1.030 | 8.5-12% | 280-350 |
| Wheat Beer | 1.044-1.052 | 1.008-1.014 | 4.3-5.6% | 140-170 |
| Porter | 1.040-1.060 | 1.008-1.016 | 4.0-6.5% | 140-200 |
Understanding Gravity Measurements
Specific Gravity (SG) compares the density of your wort to pure water (1.000). A reading of 1.050 means your wort is 5% denser than water due to dissolved sugars. As yeast consumes sugar and produces alcohol (which is lighter than water), the gravity drops. Most beers finish between 1.005 and 1.020.
Brix and Plato both measure sugar content as a percentage by weight. A reading of 12°Bx means 12% of the solution's weight is sugar. These scales are nearly identical for brewing purposes (the difference is less than 0.05% at typical brewing concentrations). Refractometers read in Brix and are convenient because they require only a few drops of liquid, but they need a correction factor after fermentation begins because alcohol affects the reading.
For post-fermentation refractometer readings, you must apply a correction formula because alcohol has a different refractive index than sugar water. Many online calculators and this tool handle this conversion automatically when you select Brix as your unit. If using a hydrometer for FG readings, no correction is needed as hydrometers measure density directly.
Frequently Asked Questions
What is a good ABV for homebrew beer?
Most homebrew beers range from 4-7% ABV. Session beers are 3-4.5%, standard ales and lagers are 4.5-6%, and strong beers are 6-12%+. The ABV depends on how much fermentable sugar is in your recipe and how completely the yeast ferments it.
Why is my ABV lower than expected?
Low ABV usually means fermentation stalled before completing. Common causes include: yeast health issues, fermentation temperature too low, insufficient nutrients, or too much unfermentable sugar in the wort. Check that your FG is stable for 3 days before concluding fermentation is done.
How accurate is the (OG-FG) × 131.25 formula?
This simplified formula is accurate within ±0.2% ABV for beers under 6%. For stronger beers (above 8%), it can underestimate ABV by 0.3-0.5%. More accurate formulas like the Balling equation account for the non-linear relationship but require more complex calculations.
What is apparent vs real attenuation?
Apparent attenuation is calculated from hydrometer readings and overstates the actual sugar consumption because alcohol is lighter than water, making the FG reading appear lower. Real attenuation (typically 5-8% lower) accounts for this and represents the true percentage of sugar consumed.
Can I use a refractometer for final gravity?
Yes, but you must apply a correction factor because alcohol changes the refractive index. Without correction, a refractometer will read higher than the actual gravity after fermentation. Use a refractometer correction calculator or this tool's Brix mode which handles the conversion.
How many calories are in craft beer?
Calories in beer come from both alcohol and residual carbohydrates. A typical 5% ABV beer has about 150-170 calories per 12oz serving. Higher ABV beers have proportionally more calories — a 9% imperial IPA can have 280+ calories per serving. Light beers (3.5-4% ABV) typically have 90-110 calories.