They are different species of plant, not different grades of the same one.
Arabica
Grown at higher altitude, more difficult and more susceptible to disease. Lower caffeine, higher sugar and lipid content, and a far wider range of aromatic compounds.
Tastes sweeter, more acidic and more complex, with the origin character that makes specialty coffee interesting. Roughly 60 per cent of world production and essentially all of specialty.
Robusta
Grown lower, hardier, higher-yielding and cheaper. Around twice the caffeine, less sugar, more chlorogenic acids.
Tastes harsher, more bitter, woody or rubbery at low grades, with little of the delicacy arabica offers. It also produces markedly more and thicker crema.
Why robusta persists
Three reasons, and only one of them is cynical.
Cost. It is substantially cheaper, which is why it dominates supermarket blends and instant coffee.
Crema and body. Traditional Italian espresso blends often include 10 to 20 per cent robusta deliberately, for the thicker crema and the heavier body that stands up to milk. That is a legitimate craft choice, not a cost saving.
Caffeine. If you want a stronger hit, robusta delivers it.
Fine robusta
A small specialty movement is producing carefully grown and processed robusta that is genuinely good — sweet, heavy and chocolatey rather than harsh. It is still rare and worth trying if you find it.
What to look for
A bag stating “100% arabica” is telling you it contains no robusta, which at the supermarket end is a meaningful signal. At the specialty end it is assumed and rarely mentioned.
Questions people actually ask
Does robusta really have twice the caffeine?
Roughly, yes — about 2.2 to 2.7 per cent by weight against arabica’s 1.2 to 1.5. That is also part of why it tastes more bitter.
Is robusta in my blend a bad sign?
Not necessarily. A named percentage in a traditional Italian espresso blend is a deliberate choice for crema and body. An unnamed cheap blend is usually robusta because robusta is cheap.
Last reviewed 8 August 2026