Beer Glossary: Brewing, Testing and Tasting Terminology

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Alcohol Content
Alcohol content is measured in percent. The percentage may be either by volume or weight. Since alcohol is lighter than water, the %volume number is larger than the %weight number by a factor of 1.25. Beer in the US is commonly measured in %weight (e.g., 3.2% beer has at most 3.2% by weight of alcohol, or 4% by volume).

Original Gravity (OG)
The measure of malt sugars in a brew taken before fermentation. This measure is called the Specific Gravity (see below). The primary contribution to Specific Gravity is sugar, some of which is fermented into alcohol, and some of which remains in the finished beer to give sweetness and body.

Specific Gravity (SG)
Specific Gravity measures the amount of sugar in a solution, or in our case a brew. A brew’s Specific Gravity is its density relative to water. Wort (unfermented beer) has a specific gravity greater than water due to the presence of sugars. Beer has a specific gravity less than wort because some of the sugars have been fermented into alcohol. Using a hydrometer, the specific gravity of water is 1.000 and as you add sugar and other soluble materials, the hydrometer floats higher in the solution giving a higher reading (e.g. 1.030, 1.040, etc.). As the sugar is converted to alcohol, the hydrometer sinks lower and the reading gets less. The Specific Gravity of most beers will start in the range of 1.040 to 1.055. When fermentation is finished we call the specific gravity the Final Gravity (FG).

Final Gravity (FG)
The Final Gravity is the Specific Gravity of the fermented beer. It will always be less than the original gravity because during fermentation heavy sugars are converted to lighter carbon dioxide and alcohol. The gravity is reduced both by the reduced sugar content, and because alcohol is lighter than water. The Specific Gravity of most beers will start in the range of 1.040 to 1.055. The Final Gravity will usually range from 1.006 to 1.018. The higher the Final Gravity the more body the beer will have.

International Bitterness Units (IBU)
A system of indicating the hop bitterness in finished beer. A light American lager may have around 10 IBU’s, an English mild ale around 20 units, an India Pale Ale 40 or higher, an Irish stout 55 to 60 and barley wine 65.

Plato Scale
Professional brewers often use the Plato (oP) scale, instead of specific gravity, as a measure of the sugar levels in wort and beer. Very roughly, a 1.004 Specific Gravity (SG) is equivalent to 1° Plato (1% sucrose) and 1.040 to 10° Plato (10% sucrose). In other words, each Plato degree accounts for 0.004 Specific Gravity. To convert Specific Gravity to Plato, divide the digits to the right of the decimal point by 4. For example, 1.044 is 11° Plato and 1.054 is 13.5° Plato. There will not be a quiz on this.

Standard Reference Method (SRM)
Beer color in the US is measured by the Standard Reference Method (SRM) or in Degrees Lovibond (degL). The numbers are about the same between the two scales, and they tend to be used interchangably. Higher values of the color measurement correspond to darker beers. The scale is not linear: 10SRM is not twice as dark as 5SRM, for example. The Europeans (and most of the rest of the world) use a different scale called EBC. To find the EBC equivalent on an SRM scale, take the SRM and multiply by 2.65, then subtract 1.2. This is approximated, but very close.

Fermentation
Fermentation is the transformation of carbohydrates to carbon dioxide and alcohol by yeast.

Wort
Unfermented beer. Wort, pronounced wert, is the liquid extracted from the mashing process during the brewing of beer (or whiskey). Wort contains the sugars that will be fermented by the brewing yeast to produce alcohol.

Yeast
Yeast are fungus cells that eat and drink the sugars, proteins and water found in wort. The waste of yeast help to produce the various smells and flavors found in beer, as well as creating carbon dioxide and ethanol production.