Coffee grinder adjustment - How, when and why?

Grinder Adjustment

Calibrating your commercial coffee grinder is something that should be done every morning prior to opening and should also be monitored throughout the day, particularly in erratic weather conditions. Many cafes and espresso bars ignore this procedure and the result is inconsistent and poor tasting espresso.

As coffee beans warm up, they expand and it is therefore much easier to extract their oils. If the coffee is a much cooler temperature, extraction is much more difficult. Remembering your correct extraction times you will find that the warmer the weather, the warmer the beans, the finer the grind. The cooler the weather, the more course the grind needs to be.

If you have high quality coffee beans, an excellent espresso machine, and a skilled barista, but do not have the coffee grinder adjusted for current conditions, the coffee produced can be of poor quality: either under extracted, which will taste sour, watery and weak, or over extracted, which will taste bitter and burnt. In fact, most often when you consume an espresso that is of poor quality, it is that the grind was set incorrectly for the atmospheric conditions at that time. No fancy latte art can hide a poor quality espresso.

The good news is that calibrating your grind is very simple to do. Unfortunately, many coffee shops and espresso bars don't bother to do it. The skilled barista can achieve the correct result purely by sight but for the rest, all you need is a kitchen timer. A timer with a digital readout, that has easy to read large numbers are best. You may want to get a kitchen timer with an adhesive back so it can stick to the front panel of your commercial espresso machine. This way, the timer will always be visible, and handy for checking your grind throughout the day.

There is a dial on all commercial grinders that turns clockwise and anti clockwise to adjust the way the blades or burrs, cut through the coffee beans. Which way you turn will determine whether the coffee is cut fine or course. The finer the grind, the smaller the granules, the slower the extraction. If the grind is too course, the granules are much larger and the water flows through the coffee too quickly. Over extraction vs under extraction.

Fresh Coffee vs Aged Coffee

Grinder adjustment is critical when using freshly roasted coffee and is a variable that needs to be taken into account when making espresso. 

Coffee begins to emit carbon dioxide (de gas) immediately after roasting and can take at least 7 days before it begins to settle and become more stable. As coffee is a natural product, it can change quickly and dramatically during this de gassing process. Does this mean that the coffee cannot be used during this time? No. It certainly can but the grinder adjustment becomes more critical. 

Coffee bags should always display the roasting date.

Optimal Extraction Times

When timing an espresso, the age of the coffee ie the roast date, should be taken into consideration. Also, most coffee roasters will advise on the optimum timing for their own particular roast. As a general guide, the optimal espresso should be approximately 30ml in length (including crema) and should extract for approximately 27-30 seconds. 


* If the grind is correct, the flow of espresso will begin some seconds after engaging the programmed button

* Flow can be likened to a mouses tail, be rich and smooth and give a golden crema. You will notice the 'tiger stripe' on the surface of the crema

* Extraction should be 30ml over approximately 27-30 seconds

* If the coffee extracts too quickly, the grind is too course and will leave a sour taste on the sides of your tongue

* If the coffee extracts to slowly, the grind is too fine, leaving a burnt and bitter taste towards the back of your tongue

* Be sure to always clear the neck of your grinder of previously ground coffee when an adjustment is made so as not to mix the different grinds

Darren Silverman
Darren Silverman


6 Responses


August 16, 2017

I was taught that young coffee is very gassy and the water struggles to get through…so you have too much resistence in the puk….so make it coarser for young coffee.
if coffee batch is very old it dries out so it will you need to grind finer to get flavour out…???
ideally you want your coffee beans at the perfect brewing “age” ie date after roasting…. lol I am learning too :)


December 12, 2016

Hey guys, Matt Perger believes when the beans become cooler they go through a glass phase becoming brittle and are easier to grind finer… when beans in the hopper heat up they pass to a plastic phase meaning that you have to tighten up the grind to achieve the same granulometry. That would contradict what you’ve written here… any thoughts?

David Harris
David Harris

October 29, 2016

David if you are not adjusting your grind both at the start and during the day, you should not be making coffee. Simple as that!


July 01, 2016

it’s really helpful for me. I find exactly what I want.
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Your regards


February 22, 2016

I do not think daily grinder adjustment is what should be done.
Firstly, when a grinder is calibrated (set) correctly there are only 2 reasons why you would touch the setting.
1/ Natural ware of the blades requires finer adjustment as blades loose there edge.
2/ If using a dosage grinder with an auto fill ground chamber and humidity is high eg. Hot weather and thunderstorm activity is a likely cause and the pour is slow or dripping, you need to coarse up your grind until the weather stabilizes then you would need to return to the original position prior to the adjustment when humidity levels return to normal.
If using a grind on demand unit the weather should not affect the pour at all as the coffee is used immeadiately and does not sit in the chamber absorbing moisture. Playing with or adjusting the grind should be kept to a minimum, watch your pour and adjust your tamp before any grind adjustment is considered ! The main cause of bitter (under extraction) or (burnt) over extraction is mainly caused by under or over loaded filter basket or incorrect guestimate of operators using grind on demand units and not using the auto dose setting. Most importantly, if changing grind setting on auto fill flick lever grinder you need to remove all ground coffee from front chamber, make your adjustment and only grind a small amount and run a shot to see if it is pouring correctly. Saxon, if coffee is fresh and its a dark roast more oil will be released so you will need to set your grind to suit, if you are using the same coffee but it is aged you will need to set a finer grind as the water (9 bar pressure on commercial machines) will pass through drier coffee grounds easier than fresh oilier coffee grounds, here’s your target : 30ml including crema in aprox 25 min – 30 seconds, you commence timing from the moment you press the shot button. I hope this helps, good luck.


September 25, 2015

So how do you adjust your grind for fresh vs aged coffee … finer/coarser etc? What will/should it look like?

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