How to Dial In Espresso Grind Size in a Café

Written by Tiny Tiger Coffee

Picture a Saturday at a busy café. The first shot at 8 am runs in 27 seconds and tastes lovely, all chocolate and caramel in a cappuccino. "Perfect. We're ready for today's rush," you think to yourself. By 11, after a queue out of the door and a fresh bag in the hopper, the drinks have picked up a sharp edge that nobody behind the bar can quite name. A coffee that was dialled in perfectly now doesn't taste as good. What has actually happened?

The basic idea

You control a few things when making espresso:

• Dose: how much ground coffee goes in (in grams)
• Yield: how much liquid espresso comes out (in grams)
• Time: how long the shot takes to run
• Grind size: finer makes the shot slower, coarser makes it faster
• Temperature: how hot the brewing water is
• Puck prep: how evenly the coffee sits in the basket before tamping

Dialling in means pulling a shot, tasting it, changing one thing, and repeating until it tastes good. Your tongue is the final judge, not the numbers.

The step by step method

1. Look at the beans first. Light roasts are harder to extract, so start with a lower dose. Dark roasts are easier, so use a higher dose. Medium roasts sit in the middle.
2. Pick a starting recipe. For example, 18 g in, 30 to 40 g out, aiming for 27 to 30 seconds.
3. Pull the first shot just to see where you are. Don't expect it to be good.
4. Fix the grind first. If your shot came out in less than 18 seconds, it brewed too fast, so grind finer. If it takes longer than 35 seconds, it came out too slow, so grind coarser. Make small changes; a big jump can overshoot.
5. Taste every shot and adjust. Once you fix the dose and the grind size, begin tasting your coffee. Is it tasting too sour? If it is, try brewing the coffee for a couple of seconds longer. Is it tasting too bitter? Then you might be over-extracting, so reduce the brew time.
6. Stop when it tastes sweet and balanced.

What the taste is telling you

A morning dial-in routine for a café bar

This takes about ten minutes and four or five shots. Write each shot down. It may feel slow the first week, but trust us, the devil is in the details and in the process.

1. Warm everything up. Let the machine reach temperature, run a blank shot through the group, and lock in a warm portafilter.
2. Purge the grinder. Grind a few grams in the grinder to clear out any leftover coffee from yesterday.
3. Pull a shot at yesterday's setting. Weigh the dose, weigh the yield, note the time.
4. Read the time. If it is within a few seconds of your target, taste it. If it is far off, move the grind in the right direction (finer if fast, coarser if slow), purge, and pull again.
5. Taste the shot that lands on time. Taste it on its own and in a small amount of milk, since most of what you sell will have milk in it.
6. Make one final adjustment, if needed. Sour or thin: a little finer, or a couple of grams more yield. Harsh or bitter: a little coarser, or a couple of grams less.
7. Record the setting with the date and the roast date on the bag.

One more habit makes the whole routine easier: keep the hopper light. Coffee sitting in the hopper is exposed to air and to the warmth of the grinder, so it changes through the day. Put in only what you expect to use in the next couple of hours and top it up roughly every two hours, rather than emptying a whole bag in at opening.

When to dial in again during the day

A morning dial-in is not a guarantee for the whole day. Pull a check shot and weigh it whenever one of these happens:

• You open a new bag, especially if the roast date is different from the last one. Coffee also needs time to rest after roasting. In its first ten days it is still releasing a lot of carbon dioxide, which makes shots gassy and uneven and adds a sharp, extra acidity. We recommend using our medium-plus roasts from about 10 days after the roast date up to around 60 to 70 days, as long as the bags are stored well, sealed and away from heat. Even within that window, a bag on day 12 and one on day 40 can want slightly different settings.
• After the morning rush. A grinder that has just ground a few hundred grams is warmer than it was at opening, and warm burrs can change the flow.
• The weather turns. A wet, humid day and a dry one can need different settings.
• A different barista takes over. Tamping and distribution vary from person to person, and a quick check shot shows whether the change in hands has changed the shot.
• Anything is replaced or serviced: burrs, gaskets, shower screens.

We ask our café clients to re-check their dial-in at least once a day. Twice a day, at opening and again after the lunch rush, is ideal, and a bar that checks more often than that is working at a specialty level.

Channelling: how to tell you've gone too fine

There is a common belief that the finer you grind, the more you extract, so a bitter shot from a very fine grind must simply be over-extracted. Often the opposite is happening. Push the grind fine enough and the water can no longer get through the puck evenly, so it forces a few narrow channels instead. The coffee along those channels is badly over-extracted, the rest is barely touched, and the cup ends up tasting both sour and harsh at once, with a hollow middle. This is called channeling, and it is the clearest sign you have overshot.

Signs to look for:

• The shot starts slowly and then gushes in its last third.
• Streams come out unevenly, or one side of a bottomless portafilter runs pale before the other.
• The puck has small holes or cracks in it afterwards.
• The taste is sharp and bitter together, rather than one or the other.

When you see these, go coarser, even if it means the shot runs a little faster than your target. Then work on distribution and tamping, which reduce channeling at any grind setting.

How we help cafés dial in

Every bag we send has its roast date printed on it, because that date is one of the main reasons the grind setting moves. We grow and roast our coffee at Hoysala Estate in Chikmagalur, our family's certified organic and biodynamic farm, and we roast to order about twice a week, so every delivery arrives with a known roast date and can rest to the right age before it goes into the grinder. That consistency is what keeps a dial-in from needing big changes every week. Our guide to choosing a coffee supplier for your café covers the rest of what to ask a roaster.

If your shots taste wrong even after a careful dial-in, our post on why café espresso tastes bitter or sour goes through the other causes, from water temperature to a dirty group head. For brewers other than espresso, our grind size chart has settings for every method. James Hoffmann's Understanding Espresso series on YouTube is the best free deep dive we know of on each of these variables.

In summary

1. Fix the dose first and leave it alone.
2. Use grind for big changes and purge after every change.
3. Aim for 30 to 40 g out of 18 g in, in 27 to 30 seconds, then let taste decide.
4. Fine-tune with a few grams of yield rather than another grind change.
5. If a shot tastes sour and harsh at once, you have probably gone too fine. Go coarser.
6. Check again with every new bag, after the rush and when the weather changes.

If you would like help dialling in one of our coffees on your machine, message us on WhatsApp with your machine, grinder and a photo of your last shot on the scale, and we will suggest a starting point. You can also request a Café Sampler to try two to four of our café coffees first.

Common questions

What grind size is best for espresso?

There is no single number, because every grinder's scale is different. The right espresso grind is the one that gets your dose to your target yield in 27 to 30 seconds, for example 18 g of coffee to 30 to 40 g of espresso. It usually feels like fine powder with a little grit when rubbed between your fingers, finer than table salt.

Should I change the grind or the dose to fix my espresso?

Change the grind for big corrections, such as a shot running ten seconds fast or slow. Keep the dose fixed, because changing it alters how much coffee the water has to extract. Small corrections at the end are better made by pulling a couple of grams more or less espresso, which costs no purge.

Why does my espresso run faster in the afternoon?

Several things change during the day. Burrs warm up after a busy rush, a new bag may have opened with a different roast date, and humidity can shift. Pull a check shot on the scale after the morning rush and whenever you open a new bag, and adjust the grind slightly if the time has moved.

How much coffee should I purge after changing the grind?

Most café grinders hold between 5 and 20 g of ground coffee inside the burrs and chute. Purge at least that much after any change, so the next shot reflects the new setting. Your grinder's manual or supplier can tell you roughly how much it retains.