Which of these espresso variant contain more caffeine?

Question

Can you please explain what is the difference between these types of coffee and which one of them contains more caffeine then the others:

• American
• Espresso
• Lungo
• Ristretto

And please if it's possible to tell the percentage of caffeine of each one.

Answer 1

Lets's do some Espresso math:

Taking an espresso¹² as base unit, we can conclude:

• A ristretto³ uses less (typically: half as much) water than an espresso for the same amount of grounds. This means the amount of water for one serving will flow through them faster, meaning less caffeine can be extracted. (But a ristretto is quite aromatic as mostly the quickly soluble compounds get drawn out.)
• For a lungo⁴ it's the other way round, resulting in more caffeine per serving. (Typically resulting in more "bitter" compounds present.)
• An americano is an espresso "thinned" with hot water, resulting in the same caffeine amount than an espresso - because that's what went in.

So the caffeine per serving would be:

ristretto < espresso = americano < lungo

(This does not consider that all these drinks can be made with double or triple shots, but the math stays the same.)

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¹For completeness and as the question came up in comments: According to the Istituto Nazionale Espresso Italiano an espresso is made with 7g coffee per 25ml cup.

On naming:
The terms for coffee varieties all contain an ellipsis, effectively omitting the word Caffè (coffee):

² Espresso means "expressed", referring to the preparation method where water is pushed with high pressure through the grounds, as opposed to coffee from a Caffettiera or made by other methods. (Other sources claim it stands for "explicitly", meaning a cup that was prepared individually for every single guest or serving. "espresso" is the past participle of two italian verbs. Perhaps a happy coincidence.)

³ Ristretto means "restrained". Easy to remember if one keeps in mind that in the old espresso machines water was pumped manually with a long lever - one lever "pump" resulting in one cup of espresso. If the movement was restrained: voilá, a ristretto.

⁴ Lungo means "long" - see details above.

Answer 2

To say which of these has the most caffeine is a little bit complex, as it depends on if you mean how much caffeine per ounce vs. how much caffeine in the drink in its entirety. To start, let's explain the drinks.

1. Espresso

Espresso is the key to this whole discussion. Each of the four beverages you referenced is (or contains) Espresso. Espresso is a method of brewing coffee, by which pressurized water is passed through a compacted "puck" of fine grounds. In a traditional espresso shot, roughly 0.25 oz of grounds are used to create about 0.85 oz of Espresso. Caffeine levels vary depending on the coffee beans, but as a mainstream reference, Espresso made by Starbucks contains approximately 75mg (they use slightly different measurements, however).

2. Ristretto

Ristretto is a form of Espresso in which less water is used. So you take the same puck of 0.25 oz of finely ground coffee, but instead of making 0.9 oz of Espresso, you make a more concentrated 0.5 oz (or so). Because the strongest Espresso is the first to be brewed, this is the most concentrated form of espresso, and as such has the most caffeine per ounce of any drink on this list. That said, one shot of Ristretto is is less caffeinated than one shot of Espresso simply because there's less of it. As such, if measuring by the amount of caffeine per shot, this is the least caffeinated drink on this list.

3. Lungo

Lungo is the exact opposite of Ristretto. Instead of being an Espresso made with less water, it's an Espresso made with twice the water. As such, a single shot of Lungo has the most overall caffeine of any drink on this list, but is less concentrated than either standard Espresso or Ristretto.

4. Americano

This is Espresso with water in it. No, really. A solo Americano has the exact same amount of caffeine as a solo Espresso, however it is watered down, and as such is the least concentrated drink on this list. You could hypothetically make an Americano from Ristretto or Lungo shots instead of standard Espresso, and in doing so make it less or more caffeinated (respectively).

In Summary

Assuming all are made with the same number of shots, the most caffeinated drinks overall are:

1. Lungo
2. Espresso / Americano (tied)
3. Ristretto

The most caffeinated drinks per oz are:

1. Ristretto
2. Espresso
3. Lungo
4. Americano

Answer 3

By American, you are probably meaning Caffè Americano, which literally means American coffee. This is actually more of an Italian coffee since this is Italian itself. It is brewed by:

prepared by brewing espresso over hot water

Quote also from above link. So espresso is also in American coffee. Caffeine will vary as the amount of shots used will vary per person.

Espresso is coffee that is brewed by and is:

is coffee brewed by forcing a small amount of nearly boiling water under pressure through finely ground coffee beans.

It has one of the most highest amount of caffeine of any other coffee drink per unit volume, so you would expect American and any type of coffee involving espresso will lots of caffeine. Well that depends on how much coffee you are drinking as espresso is served in smaller portions.

There's no such thing as Espresso Lungo, it's actually just called Lungo. Another Italian coffee, this coffee is and is brewed by:

Lungo is Italian for 'long', and refers to the coffee beverage made by using an espresso machine to make an Italian style coffee - short black with much more water, resulting in a stretched coffee, a lungo.

Now don't be fooled by this as to make this coffee, you need an espresso machine to make this creation. You just need more-than-normal amount of water and short black (single or double dose or shot). This coffee will have less caffeine than the above coffee types.

Ristretto is more of the opposite of Lungo. It uses regular ground coffee with less-than-normal amount of water:

Ristretto is traditionally a short shot of espresso coffee made with the normal amount of ground coffee but extracted with about half the amount of water... The opposite of a ristretto is a lungo, which is typically double the shot volume.

It is also Italian and literally the opposite of a Lungo. It also has less caffeine than American or espresso since it only uses a short shot of espresso and regular ground coffee, similar to Lungo.

So, American and espresso have the highest caffeine content out of the four, and Lungo and Ristrtto have less caffeine than the above. I would say that espresso has the highest of all in fact but American still looks pretty high in caffeine too.