Porter vs Stout: History, Differences and Sub-Styles

Portervs Stout

Porter and stout are both dark, roasty ales, and stout started life as a stronger version of porter: the original name was "stout porter." Today the usual difference is that stouts lean harder on roasted flavors (often from roasted unmalted barley) and tend to be darker and more bitter, while porters stay a little more chocolatey and malt-balanced. In practice the two overlap, and a brewer's choice of name is often as much tradition as chemistry.

Porter appeared in London in the early 1700s as a hoppier, aged version of the brown beer that was popular at the time. The usual story, repeated in the BJCP guidelines, is that it was named for its popularity with the street and river porters who carried loads around the city.

It became one of the most important beers in the world. Porter was widely exported in the early 1800s, but by the 1870s it had shifted toward a weaker, unaged beer, and by the 1950s it had all but disappeared from Britain. Craft brewers revived it in 1978.

Brewers made stronger versions of their porter and called them stout porters, "stout" being an old word for strong. Over time the second word dropped off. The BJCP calls porter the predecessor of all stouts.

Irish brewers then took the beer in their own direction. In the late 1800s Irish stout separated from London stout by leaning on darker malts and roasted barley. That roasted barley, which is unmalted barley roasted until black, is the ingredient most often cited as the dividing line today: it gives a sharp, coffee-like, dry roast that many porters lack. It is a useful rule of thumb, not a law. Plenty of porters use some roasted barley and plenty of stouts do not.

	Porter	Stout
Roast	moderate	moderate to strong
Signature grain	chocolate and brown malts	roasted barley (in many styles)
Flavor lean	chocolate, caramel, toffee	coffee, dark chocolate, roasted grain
Color	dark brown to near black	near black to black
Bitterness	moderate	moderate to high

The Brewers Association numbers show the overlap clearly. Its robust porter runs 5.1 to 6.6% ABV and 25 to 40 IBU; its classic Irish-style dry stout runs 4.1 to 5.3% ABV and 30 to 40 IBU. A drinker handed one of each blind would probably struggle more than they expect.

Dry Irish stout. Black, roasty, dry and relatively low in alcohol (BJCP: 3.8 to 5% ABV). Traditionally a draught beer and today usually served on nitrogen, which gives the creamy body and long-lasting tan head. The BJCP notes regional differences: Dublin-type stouts use roasted barley and are drier and more bitter, while Cork-type stouts are sweeter and more chocolatey.

Sweet or milk stout. Made with lactose, a milk sugar that yeast cannot ferment, so it stays in the beer as body and sweetness. The style developed in England in the early 1900s. BJCP range: 4 to 6% ABV, 20 to 40 IBU. Much sweeter and less bitter than other stouts. The BJCP notes that "milk" and "cream" stout are no longer allowed as names in England, though other markets permit them. Anyone avoiding dairy should know that milk stout does contain lactose.

Oatmeal stout. Brewed with a noticeable portion of oats, which give a silky, smooth body. It was most popular in England between the World Wars and was revived by craft brewers. BJCP range: 4.2 to 5.9% ABV, 25 to 40 IBU. American versions tend to be hoppier and less sweet than English ones.

Imperial stout. Also called Russian imperial stout. A strong, intense, roasty stout, BJCP range 8 to 12% ABV and 50 to 90 IBU. It descends from strong English porters brewed for export in the 1700s, said to have been popular with the Russian imperial court. American versions tend to be more bitter and roasty; English versions show more fruit and complex malt. Imperial stout is a common base for barrel-aged beer and bourbon cask finishes.

• English porter: moderate strength, chocolate and toffee, gentle roast.
• American porter: stronger and more assertive, with more roast and American hop character.
• Baltic porter: a strong, smooth dark beer from the Baltic region, usually lager-fermented, which makes it the odd one out in the family.

Serve porters and standard stouts around 50 to 55°F, and imperial stouts a little warmer, around 55 to 60°F, so the aromas open up. See beer serving temperature. Roasted flavors pair well with grilled and smoked meat, barbecue, oysters (a famously good match for dry stout), chocolate desserts and strong cheeses. More in beer and food pairing.

For the lighter side of malty beer, see American brown ale.