# OG, FG, and ABV in Brewing

Gravity is a term commonly used in to measure the density of a liquid and determine the content of a . Specifically, we use the terms Original Gravity (OG) and Final Gravity (FG) to calculate the Alcohol By Volume (ABV) of a beer.

Original Gravity (OG) refers to the specific gravity of the beer before fermentation begins. It measures the concentration of fermentable sugars in the wort, which is the liquid extracted from malted grains during the brewing process. The OG is typically measured using a hydrometer, which is a device that measures the density of a liquid.

Final Gravity (FG), on the other hand, is the specific gravity of the beer after fermentation is complete. It represents the residual sugars and other compounds left in the beer after the has consumed the fermentable sugars and produced alcohol and carbon dioxide.

To calculate the ABV of a beer, you can use a simple formula: ABV = (OG – FG) * 131.25. This formula works for most beers, as it takes into account the difference in gravity readings and converts it to a percentage of alcohol by volume.

Let's take an example to illustrate how to use this formula. Suppose the OG of a beer is 1.050 and the FG is 1.010. Plugging these values into the formula, we get: ABV = (1.050 – 1.010) * 131.25 = 0.040 * 131.25 = 5.25%.

So, in this example, the beer would have an ABV of approximately 5.25%.

It's worth noting that the 131.25 constant in the formula is an approximation and may vary slightly depending on factors such as the type of sugar used in the brewing process. However, for most homebrewers, this approximation is accurate enough for estimating the ABV of their beers.

Calculating the ABV of a beer is a useful tool for both homebrewers and beer enthusiasts. It allows you to understand the strength of a beer and compare it to other styles or commercial examples. Additionally, it can help you track the progress of fermentation and ensure that the beer is fermenting properly.

Converting gravity to ABV is a straightforward process that involves subtracting the FG from the OG and multiplying it by the appropriate constant. By understanding this calculation, you can gain valuable insights into the alcohol content of your beer and make informed decisions about your brewing process. Cheers!

## How Do You Calculate ABV From OG And FG?

To calculate ABV (Alcohol by Volume) from OG (Original Gravity) and FG (Final Gravity), you can use a simple equation. Here's how you can do it:

1. Determine the values for OG and FG. OG is the specific gravity measurement taken before fermentation, while FG is the specific gravity measurement taken after fermentation.

2. Subtract the FG from the OG. This will give you the difference in gravity between the two measurements.

3. Multiply the difference in gravity by a conversion factor of 131.25. This conversion factor is commonly used to convert gravity to ABV.

4. The result of the calculation will give you the ABV of the fermented .

Here's the equation for reference:

ABV = (OG – FG) * 131.25

It's important to note that this equation provides an estimate of the alcohol content, as there may be variations due to factors like temperature and the specific yeast used in fermentation. However, for most practical purposes, this equation provides a good approximation of the ABV.

## What Is OG And FG In Brewing?

OG and FG are abbreviations commonly used in the brewing industry to refer to specific gravity measurements. Specific gravity is a measurement of the density of a liquid compared to the density of . In brewing, it is used to determine the amount of sugar present in the wort, which is the liquid extracted from grains during the mashing process.

OG, or original gravity, is the specific gravity measurement taken before fermentation begins. It indicates the amount of sugar present in the wort before the yeast converts it into alcohol and carbon dioxide. OG is an important measurement for brewers as it helps determine the potential alcohol content of the finished beer.

FG, or final gravity, on the other hand, is the specific gravity measurement taken after fermentation is complete. It represents the remaining sugars in the beer, as well as any other dissolved solids. FG is used to determine the sweetness, body, and overall balance of the beer. It is also used to calculate the alcohol content, as the difference between OG and FG can be used to estimate the amount of alcohol produced during fermentation.

To measure specific gravity, brewers typically use a hydrometer or a refractometer. These instruments provide a numerical value that corresponds to the density of the liquid being measured. The specific gravity is usually expressed as a decimal, with water having a specific gravity of 1.000. For example, an OG of 1.050 means the wort is 1.050 times denser than water, indicating a higher sugar content.

Different scales have been used historically to measure specific gravity, such as the Balling, Plato, and Brix scales. However, the most commonly used scale in brewing is the specific gravity scale, which is based on the density of water. This scale provides a simple and consistent way to express the sugar content of the wort and the residual sugar content of the beer.

OG and FG are important measurements in brewing that indicate the sugar content of the wort before and after fermentation. They help brewers determine the potential alcohol content, sweetness, and balance of the beer. Measured using a hydrometer or refractometer, specific gravity is expressed as a decimal and is commonly used in the brewing industry.

## Conclusion

Converting gravity to ABV (alcohol by volume) is a straightforward process that can be done using a simple equation. By subtracting the original gravity (OG) from the final gravity (FG) and multiplying it by 131.25, you can determine the approximate ABV of your beer.

The original gravity refers to the specific gravity measurement taken before fermentation begins, while the final gravity is the specific gravity measurement taken once fermentation is complete. The difference between these two measurements indicates the amount of sugar that has been converted into alcohol during the fermentation process.

It's important to note that different scales have been used for measuring the original gravity, but the equation mentioned above provides a general guideline for calculating ABV.

When using this equation, it's also worth mentioning that adding priming sugar for carbonation purposes can slightly impact the overall ABV of your beer. The amount of priming sugar used can be factored into the overall recipe to get a more accurate ABV calculation.

Converting gravity to ABV is a useful tool for brewers to determine the alcohol content of their beer and can help in achieving desired strength and flavor profiles.

Thomas Ashford

Thomas Ashford is a highly educated brewer with years of experience in the industry. He has a Bachelor Degree in Chemistry and a Master Degree in Brewing Science. He is also BJCP Certified Beer Judge. Tom has worked hard to become one of the most experienced brewers in the industry. He has experience monitoring brewhouse and cellaring operations, coordinating brewhouse projects, and optimizing brewery operations for maximum efficiency. He is also familiar mixology and an experienced sommelier. Tom is an expert organizer of beer festivals, wine tastings, and brewery tours.