The difference between a Stout and a Porter

I get asked this question all of the time and I'm not quite sure there is a really good answer. What's the difference between a Stout and a Porter?

It is an understandable question. They look more or less the same, the strength (ABV) is about the same, and gosh darn it if the flavor profiles aren't too terribly different. Every year inevitably a brewer at the Great American Beer Fest, wins a medal in one of the Stout categories and the brewer themselves describe the beer as a porter. See category 72: American Stout from last year's winner list, Dead Reckoning (great beer, by the way) by Troegs Brewing in Harrisburg won a silver medal. Check out the Troegs website, they call this beer a porter. In spite of this phenomenon, Stout and Porter are classified as two separate animals in the world of beer.

First, there are several sub categories of each style, stout has the following: dry stout, sweet (or milk) stout, oatmeal stout, foreign export stout, russian imperial stout, and american stout. The porter sub categories are as follows: brown (or english) porter, robust porter, and baltic porter.

I'm going to focus on american stout and robust porter. The following descriptions are from the BJCP guidelines. Specifically, the flavor and vital stats sections of robust porter:

"Moderately strong malt flavor usually features a lightly burnt, black malt character (and sometimes chocolate and/or coffee flavors) with a bit of roasty dryness in the finish. Overall flavor may finish from dry to medium-sweet, depending on grist composition, hop bittering level, and attenuation. May have a sharp character from dark roasted grains, although should not be overly acrid, burnt or harsh. Medium to high bitterness, which can be accentuated by the roasted malt. Hop flavor can vary from low to moderately high (US or UK varieties, typically), and balances the roasted malt flavors. Diacetyl low to none. Fruity esters moderate to none.

Vital Statistics: OG: 1.048 – 1.065
IBUs: 25 – 50 FG: 1.012 – 1.016
SRM: 22 – 35 ABV: 4.8 – 6.5%"

And from the flavor and vital stats sections of american stout:

"Moderate to very high roasted malt flavors, often tasting of coffee, roasted coffee beans, dark or bittersweet chocolate. May have a slightly burnt coffee ground flavor, but this character should not be prominent if present. Low to medium malt sweetness, often with rich chocolate or caramel flavors. Medium to high bitterness. Hop flavor can be low to high, and generally reflects citrusy or resiny American varieties. Light esters may be present but are not required. Medium to dry finish, occasionally with a light burnt quality. Alcohol flavors can be present up to medium levels, but smooth. No diacetyl.

Vital Statistics: OG: 1.050 – 1.075
IBUs: 35 – 75 FG: 1.010 – 1.022
SRM: 30 – 40 ABV: 5 – 7%"

Pretty similar, no? The only differences are that american stouts are "on average" slightly hoppier and slightly darker in color. Conventional brewing wisdom says that porters are brewed with Black patent malt and Stouts are brewed with roasted barley, but I've seen a study or two that shows only homebrewers stick to this convention, where as, commercial brewers use both malts in formulating their stouts and porters (I wish I could find that study, but alas I have not been able to).

This issue is constantly up for debate, simply use the search function at beeradvocate.com and you'll find many threads discussing this issue: see generally this post.

The history of both styles is very intertwined, for the cliff notes check out the wiki page for stout.

The only observation that I can lend after trying dozens of brews from each style, is that "on average" porters are a little smokier and generally are more likely to have that "burnt" characteristic. Stouts are more likely to have that coffee and dark chocolate flavor. BUT that is a very broad, "on average" observation.

Either way, fall is around the corner and nothing is better on a cool fall afternoon than a fresh stout or porter.

Keep it dark and roasty,

HolzBrew