Grind Size Chooser

Brew method:

Choose the brewer or recipe style you want to dial in.

Target brew time:

Use seconds for espresso, minutes for most brewers, or hours for cold brew.

Actual brew time:

Optional. Leave at zero for a first-brew starting point.

Taste check:

Choose balanced for a starting point, or record the clearest flavor issue after brewing.

Water temperature:

Use the actual brew-water setting so the next-brew notes stay repeatable.

Fine dial stop:

The coarse stop below must be greater than this fine stop.

fine

Coarse dial stop:

This number must be greater than the fine dial stop.

coarse

Fine burr-gap estimate:

Use a practical estimate; this is not a particle-distribution measurement.

µm fine

Coarse burr-gap estimate:

This estimate must be greater than the fine burr-gap estimate.

µm coarse

Current grind setting:

Enter the dial used for the latest brew within the range above.

dial

Decision	Recommendation	Why / next check	Copy
{{ row.decision }}	{{ row.recommendation }}	{{ row.detail }}

When	Action	Keep constant / observe	Copy
{{ row.when }}	{{ row.action }}	{{ row.observe }}

The colored background represents broad grind labels; the dashed edges show the selected method range and the marker is the current recommendation.

Grind size changes how quickly water can reach coffee’s soluble material and, in filter brewing, how easily water moves through the bed. Finer particles expose more surface area and usually add resistance. Coarser particles expose less area and usually let water pass more freely. That is why a grind change can alter both brew time and flavor even when the dose, water, and brewer stay the same.

Brewing methods begin in different parts of the grind range. Espresso uses a compact puck and short contact time, paper-filter brewers depend heavily on drawdown, and immersion methods can extract during a long steep without relying on bed flow. A setting called “medium” on one grinder may not match “medium” on another, so micron estimates are most useful as broad anchors rather than laboratory measurements of every particle.

Brew time: A fast finish usually supports a finer next setting; a slow finish usually supports a coarser one.
Taste feedback: Sour or thin coffee can support a finer move, while bitter, dry, or astringent coffee can support a coarser move.
Grinder calibration: A usable dial estimate needs a fine stop, a coarse stop, and approximate burr-gap values for those two points.

Taste is not a single-variable measurement. Water temperature, dose, ratio, roast, filter, agitation, channeling, and pouring technique can imitate a grind problem. The safest dial-in method is to keep the recipe stable, change the grinder once, brew again, and compare the measured time and cooled-cup flavor.

A grind recommendation is therefore a starting point for the next controlled brew, not a universal setting or a particle-size analysis. Large suggested moves deserve a smaller trial first because grinder scales are not standardized and real burr geometry may not follow a perfectly linear dial.

How to Use This Tool:

Start with the brewer and target recipe, then add measured feedback only after a real brew.

Choose Brew method and enter the Target brew time in seconds, minutes, or hours.
Enter Actual brew time after brewing. Leave it at zero for a first-brew estimate, then choose the closest Taste check.
Set the grinder’s fine and coarse dial stops, their approximate burr gaps in microns, and the Current grind setting. The coarse values must be greater than the fine values.
Read the grind band, micron estimate, and dial move together. If the warning calls the move large or outside the calibration range, change partway and measure another brew before going farther.

Interpreting Results:

Recommended microns places the next brew within a broad particle-size range; it is not a measured distribution from the grounds.
Dial target translates that estimate onto the entered grinder range and is rounded to one decimal place.
Target window shows the selected recipe time with a method-specific allowance, while the method reference range explains the model’s starting band.

The timing and taste signals can disagree. A slow but sour brew may reflect channeling, uneven wetting, a cold recipe, or another setup issue rather than a need for an extreme grind move. Keep dose, water ratio, filter, and technique fixed for the next test.

At exactly 720 microns the displayed band becomes Medium-coarse; bands use an inclusive lower edge and an exclusive upper edge. Treat the label change as a naming boundary, not a sudden sensory threshold.

Technical Details:

The recommendation is a repository-authored planning heuristic. Each brew method supplies a reference time interval and a fine-to-coarse micron interval. Target time selects a base point inside that interval, measured timing applies a bounded correction, taste applies a smaller multiplier, and grinder calibration maps the final micron value to a dial position.

Formula Core:

Target time is converted to seconds. Its position within the method interval is limited to 0 through 1, then used to interpolate from the coarse micron edge toward the fine edge.

r = clamp (\frac{t_{target} - t_{\min}}{t_{\max} - t_{\min}}, 0, 1)

m_{base} = m_{coarse} - r \times (m_{coarse} - m_{fine})

When an actual time is present, the relative timing error is capped at −0.75 to 0.75 and applied at 45% strength. The selected taste multiplier follows that correction. The result cannot fall below 70% of the method’s fine edge or above 135% of its coarse edge.

e = clamp (\frac{t_{actual} - t_{target}}{t_{target}}, - 0.75, 0.75)

m_{final} = clamp (m_{base} \times (1 + 0.45 e) \times k_{taste}, 0.70 m_{fine}, 1.35 m_{coarse})

The final micron value is linearly mapped between the entered fine and coarse burr-gap anchors. That ratio is limited to the grinder’s dial range before the target is rounded to one decimal place.

d_{target} = d_{fine} + clamp (\frac{m_{final} - m_{fine-gap}}{m_{coarse-gap} - m_{fine-gap}}, 0, 1) \times (d_{coarse} - d_{fine})

Lookup Core:

The method ranges below are model inputs, not universal brewing standards. They determine the initial time and micron intervals before timing and taste corrections.

Brew method time and micron ranges used by the grind recommendation model
Method	Reference time	Micron interval
Espresso, 1:2 ratio	25 to 32 s	230 to 360 µm
Moka pot	120 to 210 s	420 to 600 µm
AeroPress, classic	90 to 150 s	480 to 640 µm
Pour-over	150 to 210 s	550 to 750 µm
Chemex	225 to 285 s	800 to 980 µm
French press	210 to 300 s	900 to 1,150 µm
Cold brew concentrate	12 to 18 h	950 to 1,150 µm

Rule Core:

Taste multipliers and grind direction rules
Taste selection	Multiplier	Direction
Balanced or unsure	1.00	Keep the timing-adjusted value.
Too sour or sharp	0.94	Move finer.
Thin or weak	0.97	Move slightly finer.
Too bitter or dry	1.06	Move coarser.
Dry or astringent	1.05	Move coarser and reduce agitation.

Limitations and Accuracy Notes:

The micron ranges and correction weights are practical planning rules, not measurements from a particle analyzer and not an official brewing standard. The dial mapping assumes a linear relationship between two estimated burr-gap anchors, while real grinders can have nonlinear steps, wear, alignment differences, and broad particle distributions.

Water temperature is retained as recipe context; it does not change the grind calculation.
A missing actual time produces starting-point guidance with no timing correction.
A recommendation outside the entered burr-gap anchors is pinned to the nearest dial stop.
A move larger than 25% of the entered dial span triggers a large-move warning.

Worked Examples:

First pour-over estimate

A 3-minute pour-over target with balanced taste and no measured brew time starts at 650 microns, in the Medium band. With dial stops 1 and 40 mapped to 250 and 1,150 microns, the target is 18.3. The missing-time warning means the next useful action is to brew once and record the finish time.

Fast, sour espresso

A 28-second espresso target that finishes in 24 seconds and tastes sour produces about 268 microns under the same grinder calibration. The dial target is 1.8, far from a current setting of 18, so the large-move warning is more important than following the full jump in one step.