The number most quoted is 63 mg per shot. It is a reasonable average and it hides almost everything that matters. Caffeine content depends on the dose, the bean, the roast and how much of it you actually extract.
The numbers by serving
| Drink | Dose | Caffeine |
|---|---|---|
| Single espresso, 25 to 30 ml | 7 to 9 g | 60 to 80 mg |
| Double espresso, 50 to 60 ml | 14 to 18 g | 120 to 160 mg |
| Ristretto, 20 ml | 18 g | 90 to 120 mg |
| Lungo, 90 ml | 18 g | 150 to 190 mg |
| Filter coffee, 250 ml | 15 g | 95 to 120 mg |
| French press, 250 ml | 15 g | 100 to 130 mg |
| Cold brew, 250 ml | concentrate | 150 to 250 mg |
| Instant, 250 ml | 2 g | 60 to 90 mg |
The spread is not noise. It reflects real differences in bean, roast and extraction, and it is why "how much caffeine is in coffee" has no single answer.
Arabica vs robusta
Robusta contains roughly twice the caffeine of arabica by weight, around 2.2 percent against 1.2 percent. A blend with 30 percent robusta lands about 30 percent higher than a pure arabica of the same dose. This is the single biggest variable after dose, and most people never think about it.
Roast level: the myth that will not die
Dark roast does not have more caffeine. Caffeine is chemically stable at roasting temperatures and is not destroyed. What changes is mass: a dark roast loses 15 to 20 percent of its weight to water and organic matter, so 18 g of dark-roasted beans contains fewer actual coffee beans than 18 g of light roast.
Because everyone doses by weight, a dark roast delivers marginally less caffeine per gram. The difference is small, roughly 5 to 10 percent, but it is in the opposite direction from the myth. What people actually notice with dark roasts is bitterness, which they read as strength.
Extraction: how much you actually get
Coffee contains caffeine, but you do not drink all of it. Caffeine is highly water-soluble and extracts early, which is why a 30 second espresso shot already pulls 70 to 85 percent of what is in the puck. Longer contact helps a little; grind helps more, because finer particles expose more surface area.
| Method | Typical caffeine extraction |
|---|---|
| Espresso, 25 to 32 s | 70 to 85 % |
| Pour-over, 3 min | 80 to 90 % |
| French press, 4 min | 85 to 92 % |
| Cold brew, 16 h | 85 to 95 % |
This is why cold brew is the sneaky one. Long contact time plus a high ratio means a 250 ml serve can hit 250 mg while tasting smooth and unthreatening.
What this means in practice
- A double espresso is roughly one 250 ml filter coffee, despite being a fifth of the volume
- Three flat whites is over 300 mg of caffeine, well past the 400 mg daily guideline for a light adult
- If you are sensitive to caffeine at 4pm, the culprit is usually the double-shot drink at lunch, not the tea at 3pm
- Decaf still contains 2 to 6 mg per shot, which adds up if you drink four of them
Where the numbers come from
Published values vary because measurement methods differ: HPLC on brewed liquid versus calculation from green bean assay. Expect any two reputable sources to disagree by 15 percent. That is normal. Use the table above for planning, and treat specific claims of "exactly 63.4 mg" as marketing.