Robusta carries roughly double the caffeine of arabica, and Liberica roughly half. As a rough guide by dry weight of the green bean, that is about 2.2 per cent for robusta, about 1.2 per cent for arabica, and about 0.6 per cent for Liberica. What you taste as strength in the cup comes mostly from dose and brew ratio, not from species.
The species question is the one people ask. The dose question is the one that decides their morning.
The three species, by the numbers
| Species | Caffeine, per cent of green bean dry weight | Relative to arabica | Where it usually ends up |
|---|---|---|---|
| Coffea canephora, robusta | About 1.8 to 2.6 | Roughly double | Instant coffee, espresso blends |
| Coffea arabica | About 1.0 to 1.5 | The reference point | Most specialty coffee |
| Coffea liberica | About 0.6 to 0.8 | Roughly half | Traditional kopi, and now specialty |
Read those as ranges, not as facts about your particular bag. Caffeine varies with variety, soil, altitude, season and handling, and published figures for the same species disagree by a third or more. The ordering holds. The decimals do not. The wider comparison across all three is in Liberica vs arabica vs robusta.
Caffeine survives the roast
Caffeine is a stable molecule at roasting temperatures. You do not roast it away, and a dark roast is not decaffeinated by degrees.
The confusion comes from measuring by volume. Roasting drives off water and burns off mass, so a dark-roasted bean is larger and lighter than a light-roasted one from the same lot. A scoop of dark roast therefore holds fewer grams, and slightly less caffeine, than the same scoop of light roast. Weigh the coffee instead of scooping it and the question disappears.
What actually changes the caffeine in your cup
Dose, first. Fifteen grams of dry coffee holds what it holds, and the gap between a 12 g dose and a 20 g dose dwarfs the gap between two species at the same weight.
Ratio, second. How much water passes through the bed sets the concentration, and to a point how much caffeine comes out. Caffeine is highly soluble and leaves early, so most sensible brews extract most of it. A workable ratio is the fastest fix for a cup that tastes wrong.
Then grind and time, which move extraction at the margins. Commonly cited figures put a mug of filter coffee somewhere between 70 and 140 mg of caffeine, and a single espresso between 60 and 80 mg. The espresso tastes far stronger and usually carries less, because there is less of it.
Strong is a word about body
When people call a coffee strong they usually mean heavy, dark, bitter or thick. All four are matters of roast, body and concentration. None of them is caffeine.
Liberica makes the point neatly. It is the heaviest of the three in the mouth, low and full, with a weight that survives milk and cooling. It also carries the least caffeine of the three. Ours is Sarawak Liberica Long Banga Honey: honey-processed, tangerine and brown sugar over milk chocolate, with coconut underneath. Not a mild cup, and it sits under arabica for caffeine.
If you are drinking less of it
Weight matters more than species, so start with the dose. A 12 g cup instead of an 18 g one is a plain reduction, and it costs you nothing but a smaller cup. After that, a lower-caffeine species at the same weight is a real if smaller lever, and Liberica is the one that gives up no body in exchange. Decaffeination is a separate subject, and we do not roast any.
The short answers
Does Liberica have less caffeine than arabica?
Yes, roughly half, at about 0.6 per cent of green bean dry weight against about 1.2 per cent for arabica. It is the lowest in caffeine of the three commercial species, and the heaviest in body.
Which coffee species has the most caffeine?
Robusta, at roughly double arabica, around 2.2 per cent of green bean dry weight. It is grown mostly for instant coffee and for espresso blends, where the caffeine and the crema are useful.
Does dark roast have more caffeine than light roast?
Measured by weight, the two are near enough identical, because caffeine survives roasting. Measured by scoop, dark roast holds slightly less, since the beans are larger and lighter.
Why does some coffee taste stronger without more caffeine?
Strength in the mouth is body, bitterness and concentration, all set by roast and brew ratio. Caffeine is bitter, but it accounts for only a small share of the bitterness in a cup.
