This Calculator finds your ABV based off your initial and final gravity readings.
Make sure to check out the legend at the bottom of this page for more information about each field and the formula’s driving all of the below calculations. (If you’re into that kind of thing)
About The Calculator
The above calculator uses your own measurements for Original & Final gravity to determine your homebrewed beers Average Alcohol By Volume.
When you are using a hydrometer to take these initial measurements, you are essentially measuring the specific gravity(SG) of your beers density as is relative to water.
This works because alcohol is less dense than water; so by measuring the difference in your beers density before it begins fermentation and creates the (less dense) alcohol you can then measure the alcohol change by volume. (yay math!)
Below you’ll find a quick run down on the calculations driving each of the results in the above ABV Calculator.
Over the years there have been a number of different variations of the ABV formula. Most homebrewers are probably familiar with the simplest form of the equation:ABV = (og – fg) * 131.25
This above equation is simple enough to remember, jot down and solve on a scrap piece of paper, but it’s not quite as accurate as some of the other ABV formula’s that are out there.
If you aren’t too concerned with the exact ABV of your brew the above calculation should suffice just fine in most cases, but for higher ABV brews in particular the following formula should prove a bit more accurate.ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794)
Example: Using the default values of our ABV calculator ( 1.075 OG & 1.015 FG ), Solve For ABV.
1.) ABV = (1.075 – 1.015) * 131.25 = 7.88%
2.) ABV = (76.08 * (1.075-1.015) / (1.775-1.075)) * (1.015 / 0.794) = 8.33%
Plato Scale Conversion
Here we convert our original gravity and final gravity values into their Plato scale values. The Plato scale values represent the percent by weight of sucrose in a given solution, or to put it more simply a 1% Sucrose solution is equivilent to a 1 °P value.°P = (-463.37) + (668.72 × SG) – (205.35 × SG2)
Example: Using our original values for OG and FG we can use the above formula to find our initial °P and Final °P values.
°P[initial] = (-463.37) + (668.72 × 1.075) – (205.35 × 1.0752) = 18.20 °P
°P[final] = (-463.37) + (668.72 × 1.015) – (205.35 × 1.0152) = 3.82 °P
Real Extract is a measurement of the sugars that are/have been fermented. The value of RE represents the density lowering effects of sugars during fermentation to alcohol.
RE = (0.1808 × °Pi) + (0.8192 × °Pf)
Example: The original gravity of our example wort is 1.075 and the final gravity measurement is 1.015 – What is RE?
RE= (0.1808 x 18.196) + (0.8192 x 3.824 ) = 6.423°P
The attenuation values shown in the ABV calculator represent the degree to which the sugar content of your beer has been fermented into alcohol. There are 2 Attenuation calculations used above:
Apparent Attenuation(AA) is an approximate value of the sugars consumed during the fermentation process.AA = 1 – [°Pf / °Pi]
While Real Attenuation(RA) is calculated using our “Real Extract” value from our previous calculation above, giving us a more accurate number to work with.RA = 1 – [RE / °Pi]
Example: Using the Initial (18.20°P) and Final ( 3.82°P) Plato values and the Real Extract value (6.42°P) of our example beer, Find AA and RA.
AA = 1 – [ 3.82 / 18.20 ] = .790
RA = 1 – [ 6.42 / 18.20 ] = .647
Once we’ve determined our ABV value of the beer, It’s fairly simple to extract our ABW percent.
ABW = (0.79 × ABV) / FG
Example: Using the ABV value we got in an earlier calculation (7.88%) and the Final gravity value measurement in our example – Find the beers ABW.
ABW = (0.79 x 7.88 ) / 1.015 = 6.14%
The below equation is essentially comprised of 3 unique formulas that when combined will give us the total estimated calorie content of our beer!
The first section in brackets calculates the known caloric contribution of ethanol using our ABW value, the second utilizes the known caloric contributions of carbohydrates.
Finally the calculated value is converted from the known caloric value per 100 ml of beer to the much more familiar standard of 12 ounces.cal per 12 oz beer = [(6.9 × ABW) + 4.0 × (RE – 0.1)] × FG × 3.55
Example: Using all of the previous calculations and their values – Determine the estimated calorie content of our example beer.
~Calories = [(6.9 × 6.14) + 4.0 × (6.423 – 0.1)] × 1.015 × 3.55 = 243.845
Or use the Beer Calories Calculator.
Frequently Asked Questions
What is the ABV Calculator?
The ABV (Alcohol By Volume) Calculator is a tool that determines the average alcohol content in homebrewed beers based on the initial and final gravity readings.
These readings are taken using a hydrometer, which measures the specific gravity of the beer’s density relative to water.
This is possible because alcohol is less dense than water, so by measuring the difference in the beer’s density before and after fermentation, the alcohol change by volume can be calculated.
How does the ABV Calculator work?
The ABV Calculator uses two main formulas to calculate the alcohol content. The simpler formula is ABV = (og – fg) * 131.25, where og is the original gravity and fg is the final gravity.
This formula is easy to remember and use, but it may not be as accurate for higher ABV brews. For more accuracy, especially for higher ABV brews, the formula ABV = (76.08 * (og-fg) / (1.775-og)) * (fg / 0.794) is used.
What is the Plato Scale Conversion?
The Plato Scale Conversion is a method to convert the original gravity and final gravity values into their Plato scale values.
The Plato scale values represent the percent by weight of sucrose in a given solution. The formula for this conversion is °P = (-463.37) + (668.72 × SG) – (205.35 × SG2), where SG is the specific gravity.
What is Real Extract and how is it calculated?
Real Extract is a measurement of the sugars that have been fermented. It represents the density-lowering effects of sugars during fermentation to alcohol.
The formula for calculating Real Extract is RE = (0.1808 × °Pi) + (0.8192 × °Pf), where °Pi is the initial Plato value and °Pf is the final Plato value.
How is the calorie content of the beer calculated?
The calorie content of the beer is calculated using the formula cal per 12 oz beer = [(6.9 × ABW) + 4.0 × (RE – 0.1)] × FG × 3.55.
This formula is made up of three unique formulas that calculate the known caloric contribution of ethanol using the ABW (Alcohol By Weight) value, the known caloric contributions of carbohydrates, and then converts the calculated value from the known caloric value per 100 ml of beer to the standard of 12 ounces.
Why is specific gravity crucial for the ABV calculator in homebrewing?
Specific gravity is a measure of the beer’s density relative to water. In the context of homebrewing, it helps determine the alcohol content of the beer.
By measuring the beer’s specific gravity before and after fermentation, brewers can calculate the change in alcohol by volume. This is because alcohol is less dense than water.
The ABV calculator uses these specific gravity readings (both initial and final) to determine the average alcohol content in homebrewed beers.
How can I ensure accurate ABV calculations using specific gravity readings?
For accurate ABV calculations, it’s essential to take precise initial and final gravity readings using a hydrometer. While the simpler formula ABV = (og – fg) * 131.25 is easy to remember and use, it might not provide accurate results for higher ABV brews.
In such cases, the formula ABV = (76.08 * (og-fg) / (1.775-og)) * (fg / 0.794) is recommended. This formula offers more accuracy, especially for beers with a higher alcohol content.
What’s the significance of the Plato Scale in the beer alcohol calculator?
The Plato Scale is a method used to convert specific gravity values into their corresponding Plato scale values.
These values represent the percentage by weight of sucrose in a given solution. In the context of homebrewing, the Plato Scale provides an alternative way to express the sugar content in the wort.
The conversion formula is °P = (-463.37) + (668.72 × SG) – (205.35 × SG^2), where SG represents the specific gravity. Using the Plato Scale can offer brewers a different perspective on the sugar content and fermentation potential of their brew.