<blockquote>
<p>Should the grind size for moka pots be as fine as that for pump espresso machines?</p>
</blockquote>
<p>No, pump espresso machines generally require a finer grind than moka pots.</p>
<p>The reason for this is that <a href="https://en.wikipedia.org/wiki/Moka_pot#Moka_coffee_characteristics" rel="nofollow noreferrer">moka pots operate at low pressure</a>, 2 bar at the most. Pump espresso machines, on the other hand, brew at a much <a href="https://knowyourgrinder.com/what-is-espresso-machine-bar-pressure/" rel="nofollow noreferrer">higher pressure of 8 to 10 bar</a>.</p>
<p>So why does this affect grind size? In moka pots you don't want to grind too fine because the device is built for low pressure. If you grind too fine and tamp it really well then the water might not pass through as well at that low pressure. That can cause the brew to take a lot longer or it might trigger the emergency pressure valve.</p>
<p>With espresso machines (assuming you're using a regular filter basket, not a pressurized one) you need that finer grind so that pressure can build up. If the grind is too coarse then the water will flow through easily at lower pressure and you don't get an <a href="https://en.wikipedia.org/wiki/Espresso#Brewing" rel="nofollow noreferrer">espresso as prescribed by some</a>.</p>
<p>Of course it's possible to brew coffee using an espresso machine at lower pressure. Instead of making an espresso, that can be used to get a <a href="https://en.wikipedia.org/wiki/Lungo" rel="nofollow noreferrer">lungo</a> using the same brew time.</p>
<hr>
<p>As posted on <a href="https://www.home-barista.com/brewing/what-is-grind-range-in-microns-for-french-press-and-slightly-coarser-t65531.html" rel="nofollow noreferrer">home-barista.com</a>, Britta Folmer's <a href="https://www.elsevier.com/books/the-craft-and-science-of-coffee/folmer/978-0-12-803520-7" rel="nofollow noreferrer"><em>The Craft and Science of Coffee</em></a> p. 313 lists an average grind size of 0.250mm for espresso and 0.300mm for stove pots (e.g. moka pots):</p>
<p><a href="https://www.home-barista.com/forums/userpix/13485_average_particle_sizes_-_the_craft_and_science_of_coffee.png" rel="nofollow noreferrer"><img src="https://www.home-barista.com/forums/userpix/13485_average_particle_sizes_-_the_craft_and_science_of_coffee.png" alt="Typical average particle sizes and fines content for different brewing methods from Britta Folmer's The Craft and Science of Coffee" /></a></p>

CC BY-SA 4.0
2022-01-14T23:20:24.370Z
What size should the grains be, exactly? I've seen 1/36" (0.8mm) recommended for espresso machines. My moka's funnel has probably that size holes, and the upper filter has even smaller holes, so I'm assuming the grind size should be no smaller than these holes.
Geremia
CC BY-SA 4.0
2022-01-14T23:27:42.773Z
@Geremia [*The Craft and Science of Coffee* cited on home-barista.com](https://www.home-barista.com/brewing/what-is-grind-range-in-microns-for-french-press-and-slightly-coarser-t65531.html) recommends median particulate size is 0.25mm for espresso. With super automatics listed at 0.35mm, I think that'd be a good starting point for moka pots also. They list 0.6mm for filter coffee, so that's really too coarse for espresso and probably on the coarse end for moka pots too.
JJJ
CC BY-SA 4.0
2022-01-14T06:13:46.323Z
2022-01-15T17:07:34.433Z
2022-01-15T17:07:34.433Z
JJJ
<p>Should the grind size for moka pots be as fine as that for pump espresso machines? I've seen some say mokas need fine grind size; others say fine/medium.</p>

CC BY-SA 4.0
2022-01-14T09:17:09.413Z
Coarser than espresso (but finer than for pour-over / filter coffee) because otherwise [this happens](https://coffee.stackexchange.com/q/3356/1118).
Stephie
CC BY-SA 4.0
2022-01-14T23:21:26.883Z
@Stephie What exactly is "this"? Accumulation of grinds in the water pot?
Geremia
CC BY-SA 4.0
2022-01-15T15:02:56.047Z
Amongst others, yes. And if the powder is too compressed by chance (because of course one shouldn’t tamp anyway) or cloggs the metal filter, you get a sort of “explosion”. Not pretty.
Stephie
<espresso-machine><moka><grind-size>
Grind size for moka vs. espresso machine
Geremia
# Grind size for moka vs. espresso machine

(Asked by: username_0 on 2022-01-13)

Should the grind size for moka pots be as fine as that for pump espresso machines? I've seen some say mokas need fine grind size; others say fine/medium.

**Tags:** espresso-machine, moka, grind-size

> **Comments:**
> **username_1**: Coarser than espresso (but finer than for pour-over / filter coffee) because otherwise [this happens](https://coffee.stackexchange.com/q/3356/1118).  
> **username_0**: @username_1 What exactly is "this"? Accumulation of grinds in the water pot?  
> **username_1**: Amongst others, yes. And if the powder is too compressed by chance (because of course one shouldn’t tamp anyway) or cloggs the metal filter, you get a sort of “explosion”. Not pretty.  

---

## 1 answers

### Answer by username_2 on 2022-01-14. Score: 3 | Accepted answer

> Should the grind size for moka pots be as fine as that for pump espresso machines?

No, pump espresso machines generally require a finer grind than moka pots.

The reason for this is that [moka pots operate at low pressure](https://en.wikipedia.org/wiki/Moka_pot#Moka_coffee_characteristics), 2 bar at the most. Pump espresso machines, on the other hand, brew at a much [higher pressure of 8 to 10 bar](https://knowyourgrinder.com/what-is-espresso-machine-bar-pressure/).

So why does this affect grind size? In moka pots you don't want to grind too fine because the device is built for low pressure. If you grind too fine and tamp it really well then the water might not pass through as well at that low pressure. That can cause the brew to take a lot longer or it might trigger the emergency pressure valve.

With espresso machines (assuming you're using a regular filter basket, not a pressurized one) you need that finer grind so that pressure can build up. If the grind is too coarse then the water will flow through easily at lower pressure and you don't get an [espresso as prescribed by some](https://en.wikipedia.org/wiki/Espresso#Brewing).

Of course it's possible to brew coffee using an espresso machine at lower pressure. Instead of making an espresso, that can be used to get a [lungo](https://en.wikipedia.org/wiki/Lungo) using the same brew time.

---

As posted on [home-barista.com](https://www.home-barista.com/brewing/what-is-grind-range-in-microns-for-french-press-and-slightly-coarser-t65531.html), Britta Folmer's [*The Craft and Science of Coffee*](https://www.elsevier.com/books/the-craft-and-science-of-coffee/folmer/978-0-12-803520-7) p. 313 lists an average grind size of 0.250mm for espresso and 0.300mm for stove pots (e.g. moka pots):

[![Typical average particle sizes and fines content for different brewing methods from Britta Folmer's The Craft and Science of Coffee](https://www.home-barista.com/forums/userpix/13485_average_particle_sizes_-_the_craft_and_science_of_coffee.png)](https://www.home-barista.com/forums/userpix/13485_average_particle_sizes_-_the_craft_and_science_of_coffee.png)

> **Comments:**
> **username_0**: What size should the grains be, exactly? I've seen 1/36" (0.8mm) recommended for espresso machines. My moka's funnel has probably that size holes, and the upper filter has even smaller holes, so I'm assuming the grind size should be no smaller than these holes.  
> **username_2**: @username_0 [*The Craft and Science of Coffee* cited on home-barista.com](https://www.home-barista.com/brewing/what-is-grind-range-in-microns-for-french-press-and-slightly-coarser-t65531.html) recommends median particulate size is 0.25mm for espresso. With super automatics listed at 0.35mm, I think that'd be a good starting point for moka pots also. They list 0.6mm for filter coffee, so that's really too coarse for espresso and probably on the coarse end for moka pots too.  

---

