Ale vs Lager: The Only Distinction That Divides All Beer

Every beer ever brewed falls into one of two families, and almost nobody can say what separates them. It is not colour, it is not strength, it is not whether the beer is craft or industrial, and it is certainly not whether it comes from Belgium or Germany. It is the yeast, and the temperature that yeast likes to work at.

The short answer

Ales are fermented with Saccharomyces cerevisiae at warm temperatures, roughly 15-24°C, in a matter of days. The warmth makes the yeast expressive: it throws off esters and phenols that read as fruit, banana, pepper and clove.

Lagers are fermented with Saccharomyces pastorianus at cold temperatures, roughly 7-13°C, over weeks, then stored cold for weeks more. The cold suppresses those same compounds, so what you taste is malt and hops with very little yeast character in between.

What the yeast is doing

Both yeasts eat sugar and produce alcohol and carbon dioxide. The difference is everything else they produce along the way, and that is governed by temperature.

Warm-fermented ale yeast works fast and produces a large quantity of secondary compounds — esters, which smell of fruit, and phenols, which smell of spice and clove. That is not a defect to be managed; in most ale traditions it is the flavour. Belgian brewing takes it furthest of anyone, deliberately fermenting hot to maximise it, which is why a Belgian ale tastes of pear and pepper before it tastes of anything else.

Cold-fermented lager yeast works slowly and produces very little of that. What is left is a clean canvas on which malt and hops are the only things showing. It is much less forgiving: with no yeast character to hide behind, any flaw in the ingredients or the process is audible.

The old shorthand — ale yeast is “top-fermenting”, lager yeast “bottom-fermenting” — describes where the yeast gathers during fermentation. It is roughly true and largely obsolete, since modern conical fermenters make both settle to the bottom.

Where lager came from

Lager is the younger of the two by thousands of years. All beer was ale until Bavarian brewers, storing beer in cold Alpine caves over the summer, found that a cold-tolerant yeast had taken over the job — and that the result was cleaner and kept better. Lagern is German for “to store”.

That yeast turned out to be a hybrid: ale yeast crossed with a cold-tolerant wild species, Saccharomyces eubayanus, which was only identified in Patagonia in 2011. Nobody bred it. It arrived, and Bavarian brewers noticed.

Refrigeration industrialised it. Once cold could be manufactured rather than found, lager could be brewed anywhere and at any scale, and it took over the world — the great majority of beer drunk today is pale lager.

What is not the difference

Four things that people reliably get wrong:

• Colour. There are jet-black lagers (schwarzbier, dunkel) and straw-pale ales (Belgian tripel, kölsch). Colour comes from malt, and malt is available to both.
• Strength. Doppelbocks are lagers at 8-10%. Session bitter is an ale at 3.5%.
• Bitterness. A pilsner is a lager and can be firmly bitter; a Belgian dubbel is an ale and is barely bitter at all.
• Quality or craft. A well-made lager is harder to brew than a well-made ale, precisely because nothing hides.

Why Belgium is almost entirely ale

Belgian brewing is built on the thing lager suppresses. Its whole identity is yeast expression — the fruit and spice of a warm fermentation, pushed further by high temperatures and alcohol-tolerant strains, and covered in why Belgian beer is so strong.

A lager brewed in the Belgian manner would be a contradiction: you would spend the money on cold storage specifically to remove the character you were brewing for. So Belgium’s own contributions — dubbel, tripel, saison, lambic, witbier — are ales without exception, and its lagers are its least distinctive beers.

The one wrinkle is the sours. Lambic and Flanders red are ales by yeast but are fermented by mixed cultures and wild organisms as well, which is a third category the two-family split does not cleanly hold. See what a lambic actually is.

The beers that break the split

Two styles sit awkwardly across the line, and both are worth knowing because they show the rule is about yeast rather than about tradition.

Kolsch and altbier are German ales fermented warm and then lagered cold for weeks. The warm fermentation makes them ales; the cold conditioning gives them a lager’s clean finish. German brewers call them obergarig lagerbier — top-fermented lager beer — which is a contradiction only if you think the categories are tribes rather than techniques.

California common runs the trick backwards: lager yeast fermented warm, because nineteenth-century San Francisco brewers had lager yeast and no refrigeration. It ferments like an ale and tastes like something in between.

Neither is a loophole. They are the proof that the variable is temperature and yeast strain, and that a brewer can mix and match them.

Side by side

What that looked like on a real list

Meyboom’s archived lists show the split neatly. The draughts opened with four lagers and a pilsner — Michelob Ultra, Carlsberg, Radeberger, Bavik Super Pils — priced at $7 to $9, and then moved into the ales: Rodenbach, St. Bernardus Wit, Delirium Tremens, Westmalle Dubbel, Chimay, Tripel Karmeliet, running $9 to $13.

That price gradient is not a coincidence. The lagers are the cheap, familiar end of a Belgian bar’s list, and the ales are what the bar is actually for. Both lists are still on the site — the beer list and the bottle list — with historical prices.

Frequently asked questions

Is a stout an ale?

Yes. So is a porter, an IPA, a wheat beer and every Belgian style of note. Dark colour has nothing to do with the family.

Is a pilsner a lager?

Yes, and it is the most influential lager there is — the pale golden style first brewed in Plzen in 1842 that the world’s mass-market beer is descended from.

Which is stronger, ale or lager?

Neither. Strength is set by how much fermentable sugar the brewer provides, not by which yeast eats it.

Why does lager take longer to make?

Cold fermentation is slow, and lagering adds weeks of cold storage afterwards. That ties up tank space and refrigeration, which is why lager is more expensive to produce than its price suggests.

Are sour beers ales?

Mostly, in the sense that they are warm-fermented — but lambic and Flanders red also involve wild yeast and bacteria, which puts them outside the tidy two-family split.

The short version

Warm yeast makes ale and gives you fruit and spice. Cold yeast makes lager and gives you clarity and nothing to hide behind. Everything else — colour, strength, bitterness, country — is a separate question, and Belgium chose ale because ale is where the flavour it wants comes from.

Related: the Belgian beer styles worth knowing and what hops actually do.