Which Hops for Irish Stout? A Practical Guide to Varieties and Dosing

The hop's job in an Irish stout is smaller than you think

Irish dry stout is a malt-and-roast beer with a hop bill that fits on one line. A classic Dublin-style dry stout lands at 1.036–1.044 OG, 4.0–4.5% ABV, final gravity around 1.007–1.011, and 30–45 IBU. That bitterness number looks high next to the gravity — a BU:GU ratio of roughly 0.8–1.1, which is American IPA territory — but in the glass it reads as dry, not hoppy, because roasted barley is doing half the work.

That has one practical consequence that should shape every decision below: you are buying alpha acid, not aroma. In a well-made dry stout, a trained taster should not be able to name the hop. Late additions, whirlpool charges and dry hopping are all optional at best and actively wrong at worst — a grassy or citrusy top note fighting 400–500 EBC of roasted barley is the single most common flaw in homebrewed stout.

Rule of thumb: one bittering addition at 60 minutes, optionally 10–15% of the hop mass at 15 minutes for a touch of texture, and nothing else.

What "clean bitterness" actually means in numbers

Two figures decide whether a hop gives you smooth bitterness or a harsh, lingering scrape: cohumulone (as % of alpha acids) and the total hop mass you have to throw in to reach target IBU.

Cohumulone is the most soluble of the alpha acid fractions and is widely associated — though the research is messier than forum lore suggests — with a sharper, more angular bitterness. In the Hopedia database of 329 varieties, cohumulone has a median of 28.5% of alpha, with the 25th percentile at 24.5% and the 90th at 39.6%. Anything under ~25% counts as genuinely low-cohumulone. That is where Challenger sits at 20–25% — bottom quartile of the entire corpus — and it is a large part of why Challenger tastes so rounded in dark beer.

The second figure matters just as much. To reach 35 IBU in 20 litres of 1.040 wort with a 60-minute boil (roughly 26–30% utilisation), you need about 26 g of 6% alpha hop but only 12 g of 13% alpha hop. Doubling the vegetal matter doubles the polyphenol load, the hop-derived astringency and the trub volume — in a beer where you already have roasted-barley tannins, that is not free. High-alpha hops are the honest choice for the 60-minute charge; low-alpha English hops are a stylistic choice you pay for in grams.

The shortlist, with real numbers

Below are the six varieties that genuinely belong in an Irish stout, with the grams you need for 35 IBU in 20 L of 1.040 wort, 60-minute boil, whole-cone/pellet utilisation assumed at ~28%. Calculate with your own mid-range alpha figure from the bag, not the catalogue range.

The spread is the point: Fuggle needs nearly four times the mass of Galena to do the same job. Using 42 g of a 0.5 ml/100 g oil hop in a 20 L batch adds meaningful grassy, woody character whether you wanted it or not.

Where these hops sit against the whole database

This is where cross-variety statistics earn their keep. Across all 329 catalogued hops the median alpha acid is 8.9%, the 75th percentile 12.5% and the 90th 15%. Galena at 12–15.5% therefore sits between the 75th and 90th percentile — genuinely high-alpha, though not extreme; the corpus maximum is 20.5%. Target, at 8.5–13.5%, straddles the median and upper quartile. Challenger's 6.5–9% is below the median for the database, and East Kent Goldings at 4–6.5% falls between the 10th and 25th percentile — EKG is, statistically, one of the weakest bittering hops still in commercial use.

Oil content tells a parallel story. The corpus median is 1.5 ml/100 g with the 10th percentile at 0.8. East Kent Goldings (0.4–1.0 ml) and Fuggle (0.44–1.0 ml) sit at or below the 10th percentile — these are quiet hops in absolute terms, which is exactly why 19th-century brewers could use them at 30+ g per 20 L without wrecking the beer. Northdown, at 1.2–2.5 ml, is the most aromatic hop on the shortlist, sitting above the corpus median and reaching the 75th percentile at its upper end. That is a reason to keep Northdown at 60 minutes only.

The humulene figures are equally revealing. Corpus median humulene is 18.5% of oil; Northdown (40–45%) and East Kent Goldings (38–44%) are both above the 90th percentile of 35.7%. Humulene oxidation products give the woody, cedar-and-tobacco tones that read as "English" — and, usefully, they are among the few hop aromatics that survive being buried under roasted barley.

Galena and Target both carry cohumulone at 36–40%, sitting between the corpus 75th percentile (35%) and 90th (39.6%). In a pale lager that would be a real concern. In a 40 IBU stout with 5% roasted barley, the perceptual difference between 25% and 38% cohumulone is far smaller than most brewers assume — roast bitterness masks the difference.

Three recipes worth of dosing, concretely

1. The pragmatic single-hop stout (what most Irish breweries actually do)

One high-alpha charge, 60 minutes, nothing else. For a 20 L batch at 1.042 targeting 38 IBU: 13 g Galena at 13% AA (~0.65 g/L) or 14 g Target at 12% AA (~0.70 g/L). This is the cleanest, cheapest and most repeatable route. Galena's fruity, dark-berry undertone is a genuine asset here — it echoes the dried-fruit notes from roasted barley rather than fighting them.

2. The traditional English-hop version

60 min: 18 g Northdown at 8.5% AA (≈30 IBU). 15 min: 10 g East Kent Goldings (≈4 IBU, plus a faint honeyed-floral lift). Total ~34 IBU, total hop load 1.4 g/L. This is the version that tastes most "old-fashioned"; the humulene-rich profile of both hops gives a cedar-and-earth backdrop that sits comfortably behind roast.

3. The soft-bitterness version for sensitive palates

If you find dry stout harsh, drop to 30 IBU and use the lowest-cohumulone hop available: 24 g Challenger at 7.5% AA at 60 minutes in 20 L (1.2 g/L). Pair it with a 90-minute mash-out-free schedule and cold-steeped roasted barley, and you will remove two harshness sources at once.

Northdown and Challenger are directly comparable here: Northdown delivers more alpha per gram but Challenger's cohumulone is up to 12 percentage points lower, which is the whole argument for using it.

Timing, form and the things that actually change the beer

• 60 minutes is enough. Isomerisation is essentially complete by 60–75 minutes; a 90-minute hop stand adds maybe 5% utilisation and more hop-derived astringency. Add at the start of a 60-minute boil and stop thinking about it.
• Skip the whirlpool. A 80 °C whirlpool addition preserves linalool and geraniol — lovely in a pale ale, muddled and soapy against 450 EBC of roast.
• Never dry hop a dry stout. If you want a hoppy dark beer you are brewing a black IPA, which is a different and legitimate beer. Say so on the label.
• Pellets over cones for the bittering charge: roughly 8–10% better utilisation and far less trub loss in a small batch, which matters when the whole hop bill is 13 g.
• Water matters more than hop choice. Target 100–150 ppm sulfate, keep chloride similar or slightly higher, and hold mash pH at 5.4–5.5 despite the roasted malt. Get residual alkalinity right and a 40 IBU stout tastes smooth; get it wrong and no hop on earth saves you.
• Age it two weeks cold. Hop bitterness in stout smooths noticeably between day 7 and day 21 in the keg.

Substitution table for when the shop is out

Recalculate by alpha acid, not by gram-for-gram swap — the alpha range across this shortlist spans a factor of five, from 2.4% at the bottom of Fuggle to 15.5% at the top of Galena.

The one-sentence version

Bitter an Irish stout with a single 60-minute addition of a mid-to-high alpha hop — around 0.6–0.8 g/L of 12–14% alpha material, or 1.2–1.5 g/L of a 6–8% English variety — aim for 32–40 IBU, and spend the effort you saved on your roasted barley, your water and your carbonation instead.