About ABV Calculator
Our free ABV Calculator turns two hydrometer or refractometer readings into the alcohol by volume (ABV) of your beer, wine, mead or cider. Enter your original gravity (before fermentation) and final gravity (after), and you get ABV, apparent attenuation and an estimated calorie count instantly.
ABV is defined as the number of milliliters (mL) of ethanol in 100 mL of solution at 20°C, the standard used for beer, wine and spirits. Making wine or mead? Try the dedicated wine ABV calculator or mead calculator, and use the refractometer calculator if you measure in Brix.
Alcohol By Volume (ABV) calculators typically utilize two primary equations to calculate the percentage of alcohol volume in a given beverage - the Standard and the Alternative equations. They differ slightly in their variables and measurement units, but both provide the means to accurately calculate ABV.
How ABV is Calculated
Standard Equation
The Standard Equation for calculating ABV is expressed as follows:
ABV = (OG - FG) * 131.25
Where:
- OG is the Original Gravity, which is the density of the wort (beer mixture) before fermentation begins.
- FG is the Final Gravity, which is the density of the wort after fermentation is completed.
- 131.25 is the empirically determined constant specifically for the ABV calculation. This constant is most used for beer: wine calculation sometimes uses a value of 136.
This equation represents the fact that the alcohol content of a beverage is directly proportional to the difference between its original and final gravity measures, multiplied by 131.25.
Alternative Equation
The Alternative Equation (Dr. Michael Hall, Zymergy, 1995, page 57, equation 18) for calculating ABV is quite similar to the Standard equation, but has a different constant used in the calculations:
ABV = (76.08 * (OG-FG) / (1.775-OG)) * (FG / 0.794)
The alternate equation tracks measured alcohol more closely for stronger beverages (roughly above 7% ABV), where the simple standard equation starts to read low. For most beers the two agree within a few tenths of a percent; for wine and mead, the alternate equation is the better choice.
Just like in the standard equation:
- OG represents the original gravity of the wort.
- FG is the final gravity.
Both equations help brewers to determine the alcohol by volume of their beverages, providing them with the vital information they need to properly label and market their products. However, depending on their specific needs and the level of precision required, brewers might opt to use one equation over the other.
Understanding Specific Gravity in ABV Calculation
Calculating the ABV of your homebrew can give you vital insights into various aspects of the fermentation process. To accurately determine the ABV, the key component you need to understand is the specific gravity.
The term specific gravity in brewing refers to the relative density of the liquid compared to water. It indicates the concentration of fermentable and non-fermentable substances in the beer, allowing brewers to assess its potential alcohol content.
An ABV or Alcohol By Volume Calculator facilitates accurate measurements of specific gravity, enabling brewers to produce consistent quality with accurate alcohol content. By comparing specific gravity readings before and after fermentation, brewers can achieve a clear understanding of their brew's ABV – an essential aspect in identifying the beer's strength and taste profile.
What is Original Gravity?
Original gravity (OG) refers to the specific gravity, or relative density, the density of the liquid extracted from the malt, before fermentation. It's used to estimate the potential alcohol content in the beer and is essentially a measurement of the total amount of soluble substances in the wort, primarily sugars but also including proteins, salts, etc. Generally, higher original gravity means more sugars, thus higher potential alcohol content.
What is Final Gravity?
Final Gravity (FG) refers to the specific gravity (density relative to water) of your beer or other fermented beverages after the fermentation process is completed. FG dramatically affects the ABV, taste, and texture of your drink.
Why is Specific Gravity Important for an ABV Calculator?
An ABV calculator relies on both the Original Gravity and Final Gravity of the brew. By comparing the ‘before’ and ‘after’ states of your brew, the calculator can compute the alcohol content. Therefore, the FG acts as an essential variable in the formula used by ABV calculators, determining the alcohol concentration in a concoction.
How to Measure Original Gravity and Final Gravity?
Measuring the Original Gravity and Final Gravity involves a simple process using a hydrometer or a refractometer. Simply collect a sample of your beer once fermentation is believed to be complete. Then, using your device of choice, record the specific gravity reading. This reading indicates your brew's Final Gravity.
Remember to always prioritize safety while brewing. Working with the right tools, a clean workspace, and being mindful of timing will deliver the best brewing results.
Ensure you're getting the most out of your homemade brew by understanding essential brewing components, like the Final Gravity, using our user-friendly ABV calculator.
What is Apparent Attenuation?
Apparent attenuation is the reduction in specific gravity of the beer wort during fermentation. It measures the percentage of sugars that the yeast consumes and converts to alcohol and carbon dioxide. It's called "apparent" because it doesn't take into account the amount of alcohol produced, which is less dense than water and can skew measurements, making it seem like more sugar is consumed than actually is. It's significant in brewing as it influences the resulting product's alcohol content, flavor, and body.
How is beer Caloric content approximated?
Calorie content in alcoholic beverages can be approximated using equations based on their specific gravity or alcohol by volume (ABV).
1. Via Specific gravity
Calories can be determined from the final gravity of the brew (once alcohol fermentation has completed). The calories from alcohol and calories from carbohydrates are summed to determine the total number of calories.
Alcohol Calories = 1881.22 * FG * (OG – FG)/(1.775 – OG)
Carb Calories = 3550 * FG * ((0.1808 * OG) + (0.8192 * FG) – 1.0004)
Total calories = Alcohol Calories + Carb Calories
This equation estimates the calories contributed by the alcohol and the residual carbohydrates left behind after fermentation.
2. Via ABV
Calories can also be estimated using ABV with this formula:
Calories = ABV * 2.5 * oz
This is a rule of thumb. Alcohol alone supplies about 1.6 calories per ounce per 1% ABV (ethanol weighs 0.789 g/mL and carries about 7 calories per gram), so the 2.5 factor also allows for the leftover carbohydrates in a typical beer. It's less accurate than the gravity method, especially for very dry or very sweet drinks.
Please note that these are all approximations and the actual calorie content may vary depending on the ingredients and the brewing process.
Also, these equations are specific to beers and similar beverages. The calorie content of spirits and wines is normally determined differently.
Method and sources
- Standard equation:
ABV = (OG − FG) × 131.25, the straight-line shortcut most homebrew software uses.
- Alternate equation: Michael Hall's published equation for alcohol by weight,
76.08 × (OG − FG) / (1.775 − OG), converted to alcohol by volume by multiplying by FG / 0.794 (0.794 is the specific gravity of pure ethanol).
- Plato: converted with a standard brewing polynomial. We checked it against the reference polynomial on Wikipedia's Brix page, and the two agree within 0.1 °P between 1.000 and 1.140.
- Brix (refractometer): the original reading is divided by a wort correction factor of 1.04 and converted to gravity. Alcohol makes a refractometer overstate the final reading, so that reading is corrected with Sean Terrill's equation, which was fitted to beers starting between 1.036 and 1.106. Confirm a final reading with a hydrometer before bottling a strong wine or mead.
- Calories from gravity: the alcohol and carbohydrate equations published by BeerSmith, per 12 US fl oz, scaled to the serving size you enter.
Every gravity-based ABV is an estimate. A lab measures alcohol directly, and its result can differ slightly from any hydrometer formula.
Sources
Happy ABV Calculating!
Whether you're brewing a pale ale, fermenting a fruit wine or racking a traditional mead, two good gravity readings are all you need. Bookmark this page, and explore our other fermentation calculators for sugar additions, temperature correction and more.