How much caffeine is in your cup

The number depends on three things

Caffeine in the cup is decided by how much coffee you used, how much of it the water pulled out, and which species the coffee was. Everything else is noise.

Dose. Caffeine is in the bean, so more grams in means more caffeine available. This is the dominant term, and it is why a mug brewed with 30 g of coffee always beats a shot made with 18 g.

Extraction. Caffeine is very water soluble and comes out early, so most brews get most of it. A long filter contact extracts more of what is there than a 27 second espresso does.

Species. Robusta holds roughly twice the caffeine of arabica. A blend with robusta in it, which is most Italian espresso, is meaningfully stronger than the same recipe in pure arabica.

Rough figures worth carrying around

Drink	Typical caffeine
Single espresso, 9 g dose	30 to 60 mg
Double espresso, 18 g dose	60 to 120 mg
Moka pot, 3 cup	100 to 150 mg
Filter or pour over, 250 ml	120 to 180 mg
Large filter mug, 400 ml	180 to 250 mg
Cold brew, 250 ml as served	150 to 240 mg
Decaf, any of the above	2 to 8 mg

These are ranges rather than values because the dose, the grind and the coffee itself all move them.

Two things people get backwards

“Dark roast is stronger.” Dark roast tastes stronger. Caffeine is thermally stable and survives roasting nearly intact. What changes is density: a dark bean has lost more water and mass, so a scoop measured by volume holds fewer beans and slightly less caffeine, while the same weight holds slightly more. Both effects are small. Weigh your coffee and the roast level stops mattering.

“Cold brew is gentle.” Cold brew tastes gentle, because the low temperature extracts fewer acids and less bitterness. The long contact time still extracts plenty of caffeine, and cold brew concentrate is often served at a higher strength than the hot coffee it replaced.

Where the ceiling is

Most health authorities put a moderate daily intake around 400 mg for adults, and around 200 mg during pregnancy. That is roughly four filter mugs, or five to six double espressos, though individual sensitivity varies more than the numbers suggest. Caffeine also has a half-life of about five hours, which is the real argument against a late afternoon cup: half of that 3pm espresso is still with you at eight in the evening.