Coffee Grind Size and Extraction

Start here if you are new

Follow this short route rather than trying to change everything at once:

1. Read the grind size chart to find a sensible starting point for your brewing method.
2. Follow how to grind coffee to make that starting point repeatable.
3. Use the bitter or sour troubleshooting guide when you have a cup to assess and a specific problem to solve.

This hub connects the variables behind a brew. For the wider choice of methods and drinks, return to brewing and recipes.

Grind size and extraction at a glance

Choose your next read by the question you need to answer. These are connected subjects, but each guide has a different job.

Use the table to pick one investigation. A useful brewing note ends with a decision, such as “keep this setting” or “test a slightly coarser grind”, rather than a list of everything that might be wrong.

Grinding: establish a repeatable starting point

A grinder produces a distribution of particle sizes, not identical little pieces. The setting influences that distribution, while the way the grounds are handled and brewed determines how water reaches them.

The complete guide to grind size and consistency is the broad reference for understanding these relationships. Read it when you want to connect grinder behaviour with brewing results rather than troubleshoot a single cup.

For the practical task, use how to grind coffee. It is the better starting point when you need a reliable routine for weighing coffee, choosing a setting and making adjustments.

What a grind chart can and cannot do

“Fine”, “medium” and “coarse” are useful relative descriptions, not universal measurements. Even a manufacturer's suggested setting is a starting point: the coffee, filter and brewing technique can require something different.

Keep the grind size chart beside your recipe when changing methods. Do not assume that a number from somebody else's grinder transfers directly to yours.

A photograph also leaves something out. Two samples can look broadly similar while containing different proportions of small particles, known as fines, and larger fragments. That distinction matters when a brew behaves differently despite an apparently familiar grind.

Adjust the grinder according to its instructions

Adjustment procedures are equipment-specific. Baratza, for example, advises running its grinders during significant moves finer when beans are present, to avoid compressing coffee between the burrs.

Follow your own manufacturer's instructions rather than applying that procedure to every grinder. Also account for retained grounds, meaning coffee left inside the grinding chamber or chute, when assessing the first dose after an adjustment.

Extraction: distinguish flavour balance from strength

Extraction is the transfer of soluble material from ground coffee into water. Strength describes the concentration of dissolved coffee material in the finished drink.

These are different questions: “How concentrated is it?” and “How much did the water take from the coffee?” Calling every unsatisfying cup “weak” hides that distinction.

Use over-extraction and under-extraction when you need to understand the terminology before changing a recipe. It is particularly useful if you have been treating stronger coffee and more thoroughly extracted coffee as the same thing.

A simple diagnostic comparison is to dilute a small portion of the finished drink with water. Dilution reduces concentration; it does not return dissolved material to the grounds. Use that comparison to ask whether excessive intensity, rather than the extraction process alone, is bothering you.

Why finer is not always better

Smaller particles offer more surface area relative to their mass. In a packed coffee bed, however, grinding finer also changes resistance to water flow.

Laboratory espresso experiments combined with mathematical modelling found that extraction yield fell again at very fine settings. The researchers interpreted this as evidence of uneven flow through the bed, rather than every particle receiving equally effective contact.

The practical lesson is limited but useful: a finer setting is not a guarantee of higher or more even extraction. Read the impact on brewing when you need to understand why an adjustment changes both flavour potential and the movement of water.

Time and consistency: read the whole brew

Brew time is an observation, not a complete diagnosis. A long drainage time might accompany restricted flow, while a different pouring pattern can change the time without any grinder adjustment.

Use extraction time and grind size when a recipe finishes earlier or later than expected. It helps frame the useful question: did the change improve the cup, or merely move the timer towards a target?

For pour-over, record total time alongside the pouring pattern. For espresso, record beverage yield alongside shot time. Otherwise, you risk comparing brews that did not actually follow the same recipe.

Consistency means predictability, not identical particles

No grinder produces perfectly uniform grounds. The useful aim is a predictable particle distribution and a repeatable brewing routine, not the elimination of every fine particle.

Read grind consistency and taste when yesterday's setting gives a different result today, or when repeated brews vary more than your adjustments explain. This is the place to investigate repeatability before chasing a supposedly perfect setting.

Separate two questions in your notes:

• Between brews: did the dose, grind setting, water and technique remain comparable?
• Within the brew: did water contact the bed evenly, or was flow restricted or uneven?

This distinction keeps “inconsistent coffee” from becoming a catch-all explanation.

Ratios and temperature: keep the recipe readable

Write filter and immersion ratios as coffee to water by weight. A ratio of 1:16 means 20 g of coffee with 320 g of brewing water, not 320 g of finished drink.

For espresso, use dry dose to beverage yield by weight. As an arithmetic example, 18 g in and 36 g out is a 1:2 ratio, not a statement about how much water entered the machine.

Read brewing ratios and temperature when you need to choose or scale a recipe. It is also the useful next step when grind adjustments have become a substitute for deciding how concentrated you want the drink.

Temperature is part of the system

Temperature affects extraction, but a kettle setting does not describe the entire brew. Grind, contact time and flow still matter.

A controlled drip-coffee sensory study compared brewing at 87, 90 and 93 degrees Celsius, adjusting other variables to hold strength and extraction comparable. It found little sensory effect attributable to brewing temperature within those conditions.

That does not mean temperature never matters. It means this experiment separated temperature from changes in extraction, something an ordinary kettle-temperature comparison may not do.

Water: check the ingredient behind every adjustment

Water hardness and alkalinity are different properties. Hardness concerns dissolved calcium and magnesium; alkalinity describes acid-neutralising capacity and influences how coffee acidity is expressed.

TDS, total dissolved solids, is another measurement again. A handheld water TDS meter estimates a value from electrical conductivity, so its reading does not identify the individual minerals present.

Start with your local water supplier's published report rather than a UK-wide hardness assumption. The Drinking Water Inspectorate advises checking with the water company because local variation can make broad maps misleading.

Use water hardness, alkalinity and TDS when the same recipe tastes different in another building, or when you need to understand filtration and machine-water requirements.

Put water standards in context

SCA Standard 102-2024, for coffee sample preparation and tasting, specifies cupping water with:

• Calcium hardness of 50 to 175 ppm as calcium carbonate.
• Alkalinity at or near 40 to 70 ppm as calcium carbonate.
• No chlorine and a pH of 6 to 8.

These are cupping specifications, not universal instructions for filling every machine. In dilute water, ppm is approximately equivalent to mg/L; “as calcium carbonate” identifies the reporting basis, not necessarily the substance dissolved in the water.

For an office machine, use the manufacturer's water requirements alongside the local report. Taste requirements and equipment protection should be considered together.

Troubleshooting taste: make one informative change

Describe the problem before choosing a fix. “Sharp and thin”, “intensely bitter” and “drying after swallowing” give you more to investigate than “bad”.

Use why coffee tastes bitter or sour for the diagnostic route. Return to over-extraction versus under-extraction if the terminology is getting in the way.

The following are starting hypotheses, not fault codes:

A repeatable comparison routine

1. Choose an established recipe. For example, Baratza's published V60 guide uses 20 g coffee, 320 g water at 98 degrees Celsius and a medium to medium-coarse grind, aiming to finish in under three minutes. These are that guide's starting conditions, not universal targets.
2. Record the baseline. Note dose, water weight, temperature, grind setting, pouring pattern, total time and taste.
3. Change the grind only. Keep your handling and recipe as similar as practical.
4. Compare the result. Record whether the original problem improved, worsened or remained.
5. Keep or reverse the change. Investigate another variable only after deciding what this comparison taught you.

The purpose of learning grind size and extraction is not to make every brew match a number. It is to make your next adjustment explainable.