This chart of beer gravities, which forms part of my ongoing exploration of the BJCP style guide, will be useful if you need a quick point of reference before brewing.
But first, what exactly is beer gravity?
When brewers talk of the gravity of beer they refer to the amount of sugar suspended in it. Because this is a value that changes as the fermentation progresses gravity is usually measured several times during the brew process.
Although quite different beers can share the same vital statistics, gravity is nevertheless one of the ways brewing organisations categorise beers.
Gravity is the beer characteristic that is most easily measured by home brewers. Floating hydrometers give you a gravity reading of any liquid.
The higher the gravity, the further out of the water they sit due to the increased density of the substance.
Types of Beer Gravity
Gravity is another way of describing the density of a liquid.
Brewers extract malt sugars to make wort, thus increasing the density of the water used. The ratio between the wort density and that of the original water is the gravity.
In general terms this is called specific gravity, but in brewing there are several sub-definitions that you should be aware of.
Immediately after mashing the wort is heavily laden with malt sugars that the yeast ferment to make beer.
Although not part of the BJCP style statistics, it’s a good idea to take a gravity reading now, before starting the boil, to see how much sugar you extracted from the mash.
This gives you an idea of your mash efficiency and lets you know if it’s worth honing your brewing process.
When you boil the wort, water is lost to evaporation and the proportion of sugar in the liquid rises.
At the end of the boil, and after cooling, take a gravity reading to find the original gravity which should be higher than the pre-boil gravity.
Original Gravity (OG) describes the amount of sugar in wort (after boiling but) before fermentation.
Yeast convert wort sugars into alcohol, gas and many other by-products that contribute to, or detract from, the final beer flavour.
As they consume this sugar the density of the beer decreases, as you would expect. The density of the liquid when fermentation is complete is the final gravity.
Final Gravity (FG) is the amount of sugar in beer after fermentation.
Beer Gravity Chart
Now that you know what gravity is you can use this knowledge in your brewing.
Gravity in beer is controlled by the quantity of malt and other fermentables in your wort. Therefore, if you have an idea of the target gravities you can begin to develop a strategy for the beer.
Many brewers use the BJCP gravities as a starting point for their recipes.
Using information from the BJCP guidance, I’ve put together this chart of original and final gravities for every beer style:
A pdf of the chart can be found here: beer gravity chart according to the BJCP Style Guide.
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For each beer in the chart, the first band of colour to the left is the final gravity, while to the right you’ll find the original gravity range.
The colours are based on an average SRM colour value for that beer style.
Beers with a final gravity towards the left of the chart will be drier on the palette; the further to the right the sweeter and fuller of body.
In terms of original gravity, the further to the right the bar, the more malt and other sugars you’ll need to start with.
You can see in the chart that the range of the target gravities is pretty large for most beer styles. This goes to show that there are many possibilities within brewing and that you shouldn’t rely too heavily on strict stylistic definitions.
Use the original gravity values as a basis for planning the malt and sugar profiles of your beer recipes, taking into account the efficiency of your system. Bear in mind that the final gravity will depend on many things, not just the amount of sugar in the wort, as explained below.
What Gravity Isn’t
Although there’s a general correlation between high gravities and strong beer, it’s not always the case. It’s the difference between the original and final gravities that’s important.
If more sugar is used by the yeast, more alcohol is produced.
Not All Sugars Are Fermented By Yeast
A variety of things affect fermentability, including type of yeast and sugar profile of the wort.
Yeast don’t consume all sugars equally; it depends on their fermentability. Some are almost 100% percent fermentable, for example cane sugar, while other sugars, such as honey, contain elements that won’t be fermented. Instead they’ll leave the beer with residual sweetness and body.
If you want a thicker beer without sweetness you can use adjuncts such as oats to add body.
Conversely, if you want a strong beer that’s still light enough to drink, use sugar as part of the grain bill. This will ferment away completely, lightening the beer at the same time.
Belgian brewers use this technique to produce strong, morish ales.
The sugars drawn from malt vary in fermentability according to the type of grain and the temperatures used to mash.
As I found out recently when testing mash schedules, it’s possible to produce two worts made of exactly the same ingredients that have different original and final gravities, and which make a (subtly) different beer.
I recommend you conduct your own experiments because the many variables really become much clearer after you’ve seen the effects in a finished pint.
A gravity chart is a great place to start when planning a beer, but the recipe itself should develop far beyond these numerical values.
Remember that the style guide is just that, a guide.
By all means use it for reference when designing beer recipes but don’t be afraid to deviate and be inventive.
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