Exploring the Evolution of Stout: Classic to Innovative Styles
Stout began as a stronger porter in 18th-century London. Here are the main stout styles today, from dry Irish to imperial, with strength and flavour for each.
In this post
The short answer: stout began in 18th-century London as a stronger (“stout”) version of porter. Today it’s a family of dark, roasty beers: dry Irish stout, sweet (milk) stout, oatmeal stout, foreign extra stout, American stout and the strong imperial stout, plus modern pastry stouts brewed with added sweets and adjuncts.
| Style | ABV | What it tastes like |
|---|---|---|
| Irish (dry) stout | 4–4.5% | Dry, roasty, light body |
| Sweet / milk stout | 4–6% | Sweeter and fuller from lactose |
| Oatmeal stout | 4.2–5.9% | Smooth, silky, mild roast |
| Tropical stout | 5.5–8% | Sweet, fruity, smooth roast |
| Foreign extra stout | 6.3–8% | Stronger, firmly bitter, roasty |
| American stout | 5–7% | Roasty with noticeable American hops |
| Imperial stout | 8–12% | Rich, intense roast, dark fruit, warming |
From porter to stout
In the late 1600s, “stout” just meant strong: you could have a stout ale or a stout beer. The dark beer it ended up attached to was porter.
| When | What happened |
|---|---|
| Early 1700s | Porter, a dark brown beer made from brown malt, becomes London’s everyday beer, probably named after the street and river porters who drank it. |
| 1700s | The strongest porters are sold as “stout porter”, soon shortened to “stout”. |
| Late 1700s | London brewers ship very strong stouts to the Baltic and Russia, where they’re popular at the imperial court: the origin of imperial stout. |
| 1817 | Daniel Wheeler patents a drum roaster for black (“patent”) malt. A little of it colours a beer brewed mostly from cheaper, more fermentable pale malt, and brown malt fades out. |
| 1800s | Guinness in Dublin becomes the best-known stout brewer. Stronger versions brewed for export to hot countries become foreign extra stout. |
| Late 1800s | Oatmeal stout is sold as a nourishing beer. |
| Early 1900s | Milk stout, sweetened with lactose, appears in England. |
| 1900s | Porter fades in Britain. Irish dry stout, later poured on nitrogen, becomes the stout most people know. |
| 1980s on | Craft brewers revive porter and oatmeal stout and add American stout, barrel-aged imperial stout and pastry stout. |
The styles by the numbers
| Style (BJCP 2021) | OG | IBU | Signature |
|---|---|---|---|
| Irish stout (15B) | 1.036–1.044 | 25–45 | Roasted barley, flaked barley, dry finish |
| Irish extra stout (15C) | 1.052–1.062 | 35–50 | A bigger, fuller Irish stout |
| Sweet stout (16A) | 1.044–1.060 | 20–40 | Lactose, full body |
| Oatmeal stout (16B) | 1.045–1.065 | 25–40 | Oats for a silky body |
| Tropical stout (16C) | 1.056–1.075 | 30–50 | High sweetness, fruity esters |
| Foreign extra stout (16D) | 1.056–1.075 | 50–70 | Strong, firmly bitter, roasty |
| American stout (20B) | 1.050–1.075 | 35–75 | Bold roast, American hops |
| Imperial stout (20C) | 1.075–1.115 | 50–90 | Big, rich, dark fruit, alcohol warmth |
Pastry stout isn’t a BJCP style. It’s usually an imperial stout with dessert ingredients like vanilla, cacao, lactose or maple.
What gives stout its flavour
- Roasted barley: unmalted barley roasted black. Sharp, coffee-like and dry; the backbone of Irish stout.
- Black (patent) malt: very dark and sharp. Too much tastes burnt or ashy.
- Chocolate malt: a softer roast with chocolate and coffee notes; common in porters and sweeter stouts.
- Flaked barley: body and the dense, lasting head.
- Oats: a silky, full mouthfeel rather than an oat flavour.
- Lactose: milk sugar the yeast can’t ferment, so it stays sweet.
Dark malts are acidic, so stouts suit moderately alkaline water. More on this in how roasted malts change flavour.
Stout vs porter today
There’s no hard line any more. Stouts usually lean on roasted barley for a sharper, drier roast; porters lean on chocolate and brown malts for a softer, more chocolatey one. Some breweries call nearly identical beers by either name. Compare our robust porter with the stouts below, or read porter vs stout.
Brew a stout at home
| Recipe | What it is |
|---|---|
| Irish stout | A light, Guinness-style dry stout, about 4%. Ready to drink quickly. |
| Dry stout | A little bigger and roastier, about 4.3% |
| Oatmeal stout | Fuller, smoother and a little sweeter |
| Deception Cream Stout | A popular community recipe for a sweet (milk) stout with lactose |
| Founders Breakfast Stout clone | An imperial oatmeal stout with coffee and chocolate, about 8% |
- Go easy on roasted barley. 8 to 10% of the grist is plenty for an Irish stout.
- Carbonate low. About 2.0 volumes for an Irish stout, or pour it on beer gas through a stout faucet for the creamy head.
- Treat big stouts like big beers. Pitch plenty of healthy yeast, aerate well, control the temperature and give them weeks to condition. See high-gravity fermentation.
Frequently asked questions
Is Guinness a stout or a porter?
Guinness Draught is an Irish dry stout. The brewery made porter before stout, and like most stouts, its stout began as a stronger porter.
Is stout stronger than other beers?
Not necessarily. Irish stout is 4 to 4.5%, lighter than many lagers. Imperial stout is the strong one, at 8 to 12%.
Why is stout served on nitrogen?
Nitrogen barely dissolves in beer, so a nitro pour gives tiny bubbles, a thick, creamy head and a softer, less prickly body.
What’s the difference between milk stout and sweet stout?
Very little. Milk stout is a sweet stout made with lactose, and most sweet stouts use it. “Cream stout” is another name for the same style.
Related guides
Porter vs stout, how roasted malts change flavour, choosing brewing malts, barrel aging and all our all-grain recipes.