The Modern Battle of Stout vs. Porter

What's the difference between porter and stout? long, quiet eras in brewing history have washed out the distinctions between the two styles, insofar as they ever were significantly different to begin with. Josh Weikert wades into to dark waters.

Josh Weikert 5 months ago


Let’s dispense with the nonsense right away: anyone who thinks the answer here is “stouts have roasted barley” can leave now.

There’s a rich blend of history and anecdote surrounding the development of porter and stout from the eighteenth through the mid-twentieth centuries, particularly as it pertains to the differences between the dark beer products of London vs. those of Dublin on the far side of the Irish Sea. Attempts to draw the dividing line based on the grist used are destined to fail since historical porters and stouts each used pale malt, brown malt, chocolate malt, patent malt, and/or roasted barley, depending on the year and the brewery.

However, there is one definitive fact we can extract from the available historical information: in the years leading up to the twentieth century, when a brewery produced both a porter and a stout, the stout was the stronger of the two beers. There also existed, for a time, a thing known as “pale stout” (not to be confused with modern interpretations of pale/white stout), and it was likewise a stronger version of pale ale. Stout, then, was an internal (brewery-specific) differentiator of relative strength and little else. “Stouts” were generally stronger, on average, than “simply porters,” even between breweries, but it wasn’t guaranteed.

Moving forward in time, though, even that meager distinction gets obliterated. By the time craft breweries get their hands on porters and stouts, there’s little meaningful difference between them anymore, which means that we’re starting (almost) from scratch. I qualify that statement only because we did (and do) have rough approximations of substyles within the broader categories of stouts and porters, as codified by the likes of the Beer Judge Certification Program. Taking a stroll down Style Guide Memory Lane, we can observe a steady coalescing of the substyles, informed by analysis of contemporary commercial examples.

Are the distinctions drawn still somewhat arbitrary? Yes, without a doubt, but they’re not entirely arbitrary. When taken as a whole, and viewed from a higher altitude with a wider lens, category-specific differences can be generally observed. Even better, the substyles are consistent (and more specific) as we progress from the initial 1997 guidelines through the revisions in 1998, 1999, 2001, 2004, 2008, and 2015. So, what might serve as differentiating variables? Let’s examine the evidence.

  • Body? Nope; both categories feature light to full-bodied substyles.
  • Alcohol? No, try again; 4 percent to double digits on both sides.
  • Esters? Maybe; porters generally don’t have to feature esters, whereas several stouts note them as being present in at least low quantities, but porters can still feature moderate esters and only the freakish Tropical Stout really “highlights” them on the stout side of the board.
  • Water chemistry? Not really; both style families note moderate-to-high carbonate content in their brewing water.
  • Yeast strain? Almost certainly not; both porters (the Baltic) and stouts (the Tropical) might use lager yeasts, whereas the others use ale strains.

There are, though, two distinctions, broadly speaking, that come to the fore: roast intensity and acidity.


Roast Intensity

First, a brief discussion of intensity vs. magnitude. For our purposes, intensity refers to where on the scale of the character of roast flavors the perception lands—from light milk chocolate at the lower-intensity end up to burnt and acrid at the higher end. Magnitude refers to how “loud” that flavor is in perception. So, for example, a beer with a hint of charred grain flavor would have a flavor high in roast intensity but low in roast magnitude. A beer with mild or smooth dark malt flavors (what you get from a Carafa Special III, for example), but lots of it, would be low in intensity but high in magnitude.

Intense roast flavors are the norm among stouts, whereas they are practically optional among porters. Only the aforementioned freakish Tropical Stout and the Sweet Stout really gloss over the roast character, and even those make mention of roast explicitly, just at a lower perceivable level. The remaining seven stout substyles indicate moderate-to-intense, acrid roast.

Not only that, but the roast intensity is not simply a function of increased strength overall—the sessionable Irish (Dry) Stout has “pronounced” roast flavor, while stronger versions exhibit the same or even optionally lower levels of roast. By comparison, the Brown and Baltic porters are described as “smooth,” “moderate,” and “restrained” in their roast character, even when that flavor is relatively strong. Even the American (Robust) Porter, which comes closest to embracing a “roasty” profile, checks up quite a bit: the description notes that it should not be “overly acrid,” suggesting a strong roast intensity, but also notes that it can feature “a bit of grainy, dark malt dryness in the finish.”

“A bit?” What kind of roasty beer can feature “a bit” of dry roast in the finish? The description of even this “roasty” porter offers the roast characters as an option, not a defining feature. Instead, the Overall Impression omits the word “roast” entirely, describing it as “a substantial, malty dark beer with a complex and flavorful dark malt character.” By way of comparison, both the Tropical and Sweet stouts invoke the “r-word” in their Overall Impressions.


Acid is also a useful differentiating factor here. Although the 2015 guidelines back off of the claim, every set of guidelines prior to that revision note that Dry (Irish) Stout often features a slight acidic note from a blended soured ale (ostensibly a feature common to Guinness beers, but also noted in others). It’s also noteworthy that the Russian Imperial Stout is specifically described as having a “slight vinous or port-like quality, but shouldn’t be sour.” That “not sour” qualification might reasonably be taken as evidence that a touch of sour character isn’t uncommon in stouts more generally, in addition to being present in the Dry (Irish) Stout particularly.


Suffice to say that there is no mention of acidity or sourness in any of the porters, beyond flat refutations: “no sourness.” This, too, might recommend to suspicion that it’s the stouts that exhibit acidic flavors, either by virtue of blended sour ale or increased acidification through the broader use of intensely roasted malts. Intense roast and slight acidity could very well be added through roasted barley—but that’s not unique.

Intense roast and acidity can be added by nearly any highly-kilned grain, so the blanket “roasted barley equals stout” claim is still not particularly robust (pun intended). While roast level alone does not provide a bright-line distinction between a porter and a stout, it is nevertheless a useful metric in tipping the scales toward one or the other. Likewise, there are few stouts or porters that would exhibit patent (or latent) sourness, but those that do might more accurately be described as stouts. These two features are not definitive as much as they are suggestive, but they provide at least some degree of utility and can be defended based on modern definitions and observations. This, however, does not prevent any brewer from using the terms interchangeably, and it should go without saying that there is substantial overlap between the two style families.

To sum up, if you’re presented with the question of, “what’s the difference between a stout and a porter,” then you’d be justified in answering “nothing” or “the spelling.” But if you’re trying to help someone differentiate between the two, you can justifiably go with “stouts are more likely to showcase more-intense roast flavors and may have a small amount of acidity.”

Unique Products

As a practical matter, brewers can call any beer a stout or a porter, if they so choose, no matter the flavor profile, ingredients used, acidity, or roast level/character. That, though, isn’t especially useful to you, our readers. In the interest of guiding your brewing, an illustration might be helpful. Below are three basic grists (assume a 5-gallon/19-liter batch size). The first is for a generic “stoutporter” (or “porterstout”). It’s a dark beer of no discernible character. Following it are variations on that recipe to more clearly differentiate them as either a stout or a porter.

The Nondescript Dark Ale
9 lb (4.1 kg) Maris Otter malt
1 lb (454 g) Crystal 40
1 lb (454 g) Chocolate malt

Nothing special there. You’ll get a 6 percent ABV dark brown beer with a generic “roasty” flavor, middle-of-the-road in both intensity and magnitude (depending on yeast and hops) balanced by some base malt character and a reasonable amount of caramel from the crystal. If we wanted to “stout up” this recipe, we could simply branch in two directions to emphasize the roast and add complexity.

The Stout
9 lb (4.1 kg) Maris Otter malt
1 lb (454 g) Crystal 40
1 lb (454 g) Pale chocolate malt
0.5 lb (227 g) Black malt

This slight variation adds a wider range of roasted flavors and increases the intensity of the roast character. Counterintuitive though it can sound, throttling down the kilning level on chocolate malts can increase their complexity since high kilning (500L+) can drive off flavor compounds. The black malt adds a sharp roasted flavor that many would associate with “stout,” and yes, you could also sub in roasted barley (both could also add a touch of perceived acidity). But what if we wanted something more patently porter-like?


The Porter
9 lb (4.1 kg) Maris Otter malt
1 lb (454 g) Crystal 80
1 lb (454 g) Chocolate rye
0.5 lb (227 g) Briess Extra Special Roast

By shifting to a “richer” caramel malt and adding more toffee flavors, we’re de-emphasizing the roasted flavors. At the same time, using chocolate rye (instead of chocolate malt or even pale chocolate, which kilns to the same Lovibond rating) adds mild cocoa dark malt flavor, but without the burnt husk, it avoids sharper roast intensity. Likewise, the Briess Extra Special Roast will emphasize “dark” but not “intensely roasty” flavors, such as prune and toffee.

Could the “stout” recipe above be reasonably called an American Porter? Certainly. Could the “porter” recipe pass as a Sweet Stout? Probably. However, we’re dealing in probabilities here. More intensely roasty is more likely to be (or be considered) a stout; less so, a porter.

A Final Hedge

To quote my hero, Edward R. Murrow, “This just might do nobody any good.” First, a quick apology to the “stout = roasted barley” faction. They’re not necessarily wrong. Assertive use of roasted barley would certainly tend, by the standard identified through the guidelines analysis above, to move a beer more to the “stout” side of the scale. We have to push back against that notion, though, because any number of porters may use roasted barley as well, so it’s simply not a useful dichotomous variable. That doesn’t mean it’s entirely without utility, however, and if you should produce a beer with 10 percent roasted barley in its grist, then you’re justified in arguing that it’s a stout.

Second, I recognize that style guidelines are just that—guidelines. They can be (and often are) rejected wholesale by brewers, and they often should be. In hunting for some kind of toehold in this debate, however, I think that focusing on them makes sense. The BJCP canvasses widely in identifying typical beers within each substyle, and while they’re often imperfect, the guidelines still represent a good-faith effort to fairly categorize and define what are often truly undefinable units.

Last, if you’re not planning to enter your beer in competition, a good bit of advice might be to answer the question, “Is this a stout or a porter?” with, “Yes.” What’s in a name, after all?


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