# What Is Espresso?

> Espresso is a brewing method defined by pressure: about 9 bar through fine grounds for 25–30 seconds. Not a bean, not a roast, not a flavour.

Topic: Espresso  
Published: 2026-08-29T10:00:00-04:00  
Updated: 2026-08-29T10:00:00-04:00  
Author: Mical Robert, Editor (https://trysix.online/author/mical-robert)  
Canonical: https://trysix.online/what-is-espresso

## The short answer

A brewing method, not a type of bean. Around 9 bar of pressure pushes hot water through finely ground coffee for 25 to 30 seconds, giving about 30 ml topped with crema. Any bean works — the pressure is what makes it espresso.

## Key takeaways

- Pressure is the definition. Around 9 bar, which is roughly nine times atmospheric pressure.
- A standard recipe is 18 g of dry coffee in, 36 g of liquid out, in 25–30 seconds.
- 'Espresso beans' are ordinary coffee beans. The label describes intended use, not a different plant.
- A single shot has about 63 mg of caffeine — less per serving than a cup of drip coffee, more per millilitre.

Espresso gets treated as a type of bean, a strength setting, or a small angry coffee. It is none of those. It is a method, defined by a specific amount of pressure — and once that clicks, most of the confusing things about café menus and bags labelled espresso resolve themselves.

## The definition

Espresso is defined by how it is made. Hot water at around 200°F is forced under roughly 9 bar of pressure through a compressed bed of finely ground coffee. The whole extraction takes 25 to 30 seconds and produces about 30 ml of liquid per single shot.

Everything people associate with espresso follows from that. The intensity comes from the ratio — about 1:2, against 1:16 for drip. The crema, that layer of reddish-brown foam, is carbon dioxide from the roasting process emulsified into the liquid under pressure. The small cup exists because 30 ml is what the method produces.

> **It is a verb, not a noun** — "Espresso" describes an action performed on coffee. There is no espresso plant, no espresso bean and no espresso species. Grind any coffee fine enough and push water through it at 9 bar and you have made espresso.

## The four numbers

**The parameters that define a shot, and what happens outside them.**

| Parameter | Standard | Too low | Too high |
| --- | --- | --- | --- |
| Pressure | About 9 bar | Weak, thin, no crema | Channelling; harsh, uneven |
| Dose | 18–20 g in a double basket | Water runs through fast; sour | Basket overfills; blocked |
| Yield | Double the dose — 36 g out | Concentrated, sharp | Watery, over-extracted, bitter |
| Time | 25–30 seconds | Under-extracted, sour | Over-extracted, bitter |

These interact. Grind finer and the water meets more resistance, so time goes up. Grind coarser and it drops. Baristas 'dial in' a coffee by holding dose and yield fixed and moving the grind until the time lands in range — the same logic as [dialling in any brew](https://trysix.online/how-to-make-a-perfect-cup-of-coffee), just faster and less forgiving.

## Why 9 bar

Nine bar is not a law of physics; it is a convention that emerged from the spring-lever machines of the 1940s and 50s and stuck because it works. Research modelling espresso extraction has found that the parameters interact in ways that make the traditional recipe less optimal than assumed, and that finer grinds do not straightforwardly mean better extraction — beyond a point, the bed channels and extraction becomes uneven.

> Reducing the mass of coffee and coarsening the grind can produce more reproducible shots at lower cost than the traditional recipe.
>
> — Cameron et al., Matter (2020)

That is worth knowing because it undercuts a lot of confident advice. The traditional numbers are a good starting point and a poor law.

## Espresso versus other coffee

The comparison that matters is concentration versus dose. Espresso is about three times as concentrated as drip coffee per millilitre, and a single serving is about one-eighth the size — so a shot delivers less caffeine than a cup of coffee, while tasting far more intense.

**Figure: Caffeine per serving, as normally served**

| Item | Value |
| --- | --- |
| Drip coffee, 8 oz (The standard reference figure) | 95 mg |
| Double espresso, 60 ml (Two shots) | 126 mg |
| Latte (2 shots + milk) (Milk adds volume, not caffeine) | 126 mg |
| Single espresso, 30 ml (Less than a cup of coffee) | 63 mg |
| Decaf espresso (Not zero) | 8 mg |

_Per millilitre espresso is far stronger; per serving it is not. Serving size does most of the work._

[Espresso vs coffee](https://trysix.online/espresso-vs-coffee) works through the comparison in full, including where the 'espresso is stronger' claim is true and where it is not.

## What crema is, and what it tells you

Crema is an emulsion: carbon dioxide trapped in the coffee during roasting, released and forced into suspension by the pressure of extraction, stabilised by coffee oils and melanoidins. It sits on top of the shot as a hazelnut-coloured foam and dissipates over a minute or two.

- Thick, persistent crema usually means fresh coffee — beans still holding CO₂ from roasting.
- Thin or absent crema usually means stale beans, too coarse a grind, or insufficient pressure.
- Robusta produces noticeably more crema than arabica, which is why traditional Italian espresso blends often include it. See [types of coffee beans](https://trysix.online/types-of-coffee-beans).
- Crema is not a quality measure. It indicates freshness and gas content, not whether the shot tastes good.

## The drinks built on it

**What each espresso drink actually contains.**

| Drink | Espresso | Added | Total volume |
| --- | --- | --- | --- |
| Espresso | 1 shot | Nothing | 30 ml |
| Doppio | 2 shots | Nothing | 60 ml |
| Ristretto | 1 short shot | Nothing | 15–20 ml |
| Lungo | 1 long shot | Nothing | 50–60 ml |
| Americano | 1–2 shots | Hot water | 150–350 ml |
| Macchiato | 1 shot | A spoon of foam | 40 ml |
| Cortado | 1 shot | Equal steamed milk | 60–90 ml |
| Flat white | 2 shots | Steamed milk, thin foam | 150–180 ml |
| Cappuccino | 1–2 shots | Equal milk and foam | 150–180 ml |
| Latte | 1–2 shots | Steamed milk, light foam | 240–350 ml |

Note what does not change: the coffee. A latte and a cappuccino from the same machine contain the same espresso — the difference is entirely milk texture and volume. [Types of coffee drinks](https://trysix.online/types-of-coffee-drinks) goes through the whole menu.

> **'Expresso' is not a mistake worth worrying about** — The word is espresso in Italian, from the past participle of esprimere — pressed out, and also made expressly for you. French uses 'express' and many English speakers say 'expresso'. It is a variant, not a different drink, and pointing it out has never improved anyone's coffee.

## Making it at home

Real espresso needs a pump capable of 9 bar, which is what separates an espresso machine from everything else in a kitchen. A moka pot reaches about 1.5 bar and an AeroPress well under that; both make excellent strong coffee and neither makes espresso. [How to make espresso at home](https://trysix.online/how-to-make-espresso-at-home) covers what each device can and cannot do, and [what is an espresso shot](https://trysix.online/what-is-an-espresso-shot) goes deeper into shot volumes and ratios.

## Frequently asked questions

### What makes espresso different from regular coffee?

Pressure. Espresso forces water through fine grounds at about 9 bar for 25 to 30 seconds; drip coffee relies on gravity over four to six minutes. The result is roughly three times as concentrated per millilitre, served in about one-eighth the volume.

### Are espresso beans different from coffee beans?

No. They are the same seeds from the same species. A bag labelled 'espresso' has usually been roasted a little darker and is often ground finer, but there is no separate espresso plant or bean type.

### Does espresso have more caffeine than coffee?

Per millilitre, about three times as much. Per serving, no: a single 30 ml shot carries roughly 63 mg against about 95 mg in an 8 oz cup of drip coffee, because the cup is eight times larger.

### What is crema?

A foam of carbon dioxide emulsified into the coffee by the pressure of extraction, stabilised by oils and melanoidins. It indicates that the beans were fresh and still holding roasting gases — it is not, by itself, a sign that the shot tastes good.

## Sources

- [Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment](https://doi.org/10.1016/j.matt.2019.12.019) — Matter (2020) (DOI 10.1016/j.matt.2019.12.019). Supports the espresso extraction parameters and the finding that the traditional recipe is not optimal for reproducibility.
- [Spilling the Beans: How Much Caffeine is Too Much?](https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much) — U.S. Food and Drug Administration. Supports the per-serving caffeine comparison between espresso and brewed coffee.
- [What Is Coffee?](https://www.ncausa.org/About-Coffee/What-is-Coffee) — National Coffee Association USA. Supports the general description of coffee brewing and the espresso method's place among them.

## Related articles

- https://trysix.online/espresso-vs-coffee
- https://trysix.online/what-is-an-espresso-shot
- https://trysix.online/how-to-make-espresso-at-home
- https://trysix.online/espresso-beans-vs-coffee-beans

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