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Tag: OG

Original Gravity

Original gravity or OG is the specific gravity reading of a beer’s wort prior to having the yeast pitched for fermentation. The original gravity reading is important because it gives the brewer an idea of how much sugar is available for fermentation and what the approximate alcohol by volume will be once fermentation completes. The original gravity reading also permits a brewer to calculate his or her brew house efficiency to determine what percentage of starches and sugars were extracted from the grain bill used to make the beer. Typically either a hydrometer or refractometer are used to take the original gravity reading.


Below is the photo of a hydrometer which is used to take original gravity readings.

Beer Hydrometed, Final Gravity Reading

Alcohol by Volume ABV

Alcohol by volume (ABV) represents what portion of the total volume of a liquid is alcohol.


To calculate the ABV of a beer,  you will want to subtract the Final Gravity from your Original Gravity and multiply by 131.


The following is an example of how to calculate your alcohol by volume, assuming that your original gravity was 1.055 and your final gravity reading was 1.012.


Here is an example: 1.055 – 1.012 = 0.043 x 131 = 5.633%
In this example your alcohol by volume worked out to 5.633%.