I found this grind comparison chart earlier in the year while browsing around online and thought that I would share it with all of you who may make your coffee at home (you know, like when Pascal’s is closed…). Here’s a crash coarse in coffee grind and how it effects your brew. Special thanks goes to Michael Smith at INeedCoffee.com and photographer Carl Melville for allowing us to reproduce this incredibly helpful guide.
 
Coarse Grind

Coarse grind is typically used with your French press or press pot coffee maker. This is the brewing method with a container (often glass) with a filter/mesh plunger to force grinds to the bottom of the container, allowing for a clean poor with no debris (hopefully!)
 

 
Medium Grind

Coarse grind should be used for brew processes such as pour over (like the coffee maker you have on your kitchen counter). This is the process where water is dispensed at a given flow rate and volume over loose grounds, usually in a coffee filter.  Notice the difference in size from the coarse grind.
 

 
Fine Grind

Fine grind is your espresso grind. Fine grind exposes more surface area to water, allowing the water to pull more of the oils from the coffee. Though this opens up a whole new level of aroma and flavor profiles in the cup, the fine grind also increases the likelihood of over-extraction, leading to harsh and bitter flavors in the cup. In the espresso process fine grinds or tightly compacted in the portafilter to slow the passage of water through the grinds and allow the optimum amount of time for oil transfer. Think of it like sand vs. rocks. Water will pass more quickly through rocks (the coarse grind) than it will the sand (the fine grind). If you happen to use the Turkish method or hear of a place serving turkish coffee, the beans are ground to an even finer particle than what you see below.
 

 
Finally, here’s a side by side comparison of all three types.
 

 
A Final Note on Grind Quality

Remember that these are starting points, not set-in-stone standards. Play with the grind coarseness or fineness to see what different flavors are extracted. Coffee is a finicky substance and really needs to be experimented with to get the best flavor from your beans. Some coffees may benefit more or less from a change in grind quality, volume of water, speed of extraction, etc. Coffee is a science. A delicious, delicious science. So keep experimenting, and let us know what you find!