Grind Size Chooser

Grind Recommendation

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Method:

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

Target brew time:

Enter the recipe contact time, such as 30 sec for espresso or 4 min for pour-over.

Actual brew time:

Optional: enter the time from start to finish, or leave blank for a starting range.

Taste check:

Choose balanced for a baseline, or bitter/sour/weak/astringent after tasting a brew.

Water temperature:

Enter brew water temperature in C or F; small 1-2 degree moves are easiest to repeat.

Grind dial range:

Enter the lowest and highest usable numbers printed on your grinder.

Fine stop:

Smallest usable dial number, often near espresso zero.

Coarse stop:

Largest practical dial number before the grind is too coarse to use.

Burr gap estimate:

Use approximate burr openings in microns for the fine and coarse dial stops.

Fine gap:

micron

Minimum 100 microns; adjust in 10-micron steps.

Coarse gap:

micron

Minimum 200 microns and should stay above the fine gap.

Current grind setting:

Optional: enter your last dial number to get a finer/coarser move estimate.

dial

Grind guidance
Item	Recommendation	Details	Copy
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Action	When	Execution note	Copy
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Brew marker	Current value	Copy
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Grind size controls how quickly water reaches the soluble material inside coffee particles. Finer grinds expose more surface area, slow flow through a bed, and usually extract faster. Coarser grinds reduce resistance and suit longer contact times, but they can taste thin when the brew finishes before enough sweetness and body are extracted.

Different brewers need different starting points because pressure, paper thickness, immersion time, and agitation change how water moves through the grounds. Espresso works in seconds and needs a fine, tight bed. A pour-over or AeroPress sits closer to the middle. French press and cold brew rely on longer contact, so they can use a more open grind without turning the cup muddy.

The preset ranges overlap because coffee recipes overlap, but the contact-time pattern still gives a useful starting map.

Micron numbers and grinder dials are only approximations. Burr shape, roast level, dose, brew ratio, fines, filter type, agitation, and water chemistry can all shift the result. The value of a grind chooser is repeatability: it gives you a defensible first setting, then turns timing and taste feedback into smaller next moves.

Use the recommendation as a starting baseline, then change one variable at a time. If the cup is sour, sharp, or weak and the brew ran fast, a finer grind is often the cleanest first adjustment. If the cup is bitter, dry, harsh, or the drawdown dragged, a coarser setting usually deserves the next test.

How to Use This Tool:

Describe the brew you are trying to dial in, then compare the summary with the table and grind map before changing your grinder.

Choose Method. The method sets the reference brew-time range and micron band for pour-over, Chemex, AeroPress, espresso, moka pot, French press, or cold brew concentrate.
Enter Target brew time in seconds, minutes, or hours. The summary should update to a grind band, micron estimate, dial target, and target time badge.
Add Actual brew time after a real brew when you have one. A fast brew pushes the next recommendation finer; a slow brew pushes it coarser.
Set Taste check after tasting the cup. Balanced keeps the grind steady, while sour, bitter, weak, or harsh feedback adds a small correction.
Open Advanced when you want dial guidance tied to your grinder. Enter the dial range, burr-gap estimates, current grind setting, and water temperature.
Read Grind Guidance first. It shows the grind level, dial target, brew-time window, actual-versus-target timing, taste focus, and water temperature note.
Use Grind Band Map, Dial-In Playbook, and Brew Trace when you need a visual position, a next-brew checklist, or a compact record of the current setup.

If a number is missing or outside the allowed range, fix that input before trusting the recommendation. A zero target time cannot produce useful guidance, and a coarse burr-gap estimate must stay above the fine-gap estimate for dial mapping to make sense.

Interpreting Results:

The summary tells you the next grind target, not the final truth about the coffee. Give the most weight to the recommended micron band, the dial move from your current setting, and the actual-versus-target time note. Then check whether the taste cue agrees with the timing cue.

How to interpret grind size chooser outputs
Output cue	Practical reading	Check before changing
Fast actual time	The bed likely offered too little resistance for the target.	Try finer first, then retest with the same dose, ratio, and pouring pattern.
Slow actual time	The bed likely held water too long or trapped fines.	Try coarser and reduce agitation before changing temperature or ratio.
Sour or weak taste	The cup may be under-extracted or too dilute for the recipe.	Use the taste row and brew-time row together; do not chase flavor from one sip alone.
Bitter or harsh taste	The cup may have too much late extraction, fines migration, or agitation.	Coarsen in small steps and keep water temperature changes modest.
Dial target looks surprising	The micron-to-dial translation depends on your entered range and burr-gap estimates.	Verify the fine stop, coarse stop, and current setting before moving the grinder.

A close result is more useful than a dramatic move. If the tool recommends a very large change, make a smaller adjustment first, brew again, and use the new actual time as the next data point.

Technical Details:

Grind guidance begins with a brew-method profile. Each profile defines a normal target-time range, a default target time, a micron range, a small timing slack value, and a reference water temperature. The profile does not claim that every grinder produces the same particle distribution. It supplies a repeatable reference band so timing and taste can be interpreted in the same units.

The base recommendation uses linear interpolation across the method's time range. A target near the fast end remains closer to the coarse edge of the method band. A target near the slow end moves toward the fine edge. The measured brew time then adjusts that value by a capped percentage, and the taste cue applies a small multiplier. The final number is clamped to a wider method-specific envelope so an extreme timing entry does not produce an implausible grind.

Formula Core

The base micron estimate moves from the method's coarse edge toward its fine edge as the target time moves through that method's reference window.

m_{base} = m_{coarse} - \frac{t_{target} - t_{\min}}{t_{\max} - t_{\min}} \times (m_{coarse} - m_{fine})

The timing correction uses the measured timing error, capped between -75% and +75%, so a fast brew tightens the recommendation and a slow brew opens it.

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

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

The dial suggestion maps the final micron value between your entered burr-gap limits and your grinder's dial limits.

d_{target} = d_{\min} + \frac{m_{final} - g_{fine}}{g_{coarse} - g_{fine}} \times (d_{\max} - d_{\min})

Variables used by the grind size formulas
Symbol	Meaning	Unit or range
`m_fine`, `m_coarse`	Fine and coarse micron edges for the selected brew method.	Microns
`t_min`, `t_max`	Reference brew-time range for the selected method.	Seconds
`k_taste`	Taste multiplier: balanced 1.00, sour 0.94, bitter 1.06, weak 0.97, harsh 1.05.	Multiplier
`g_fine`, `g_coarse`	Estimated burr-gap microns at the fine and coarse dial stops.	Microns
`d_min`, `d_max`	Lowest and highest usable numbers on the grinder dial.	Dial units

Brew method profiles used by the grind size chooser
Method	Reference time	Micron band	Technical intent
Pour-over	150 to 210 sec	550 to 750 microns	Paper-filter flow with enough resistance for even drawdown.
Chemex	225 to 285 sec	800 to 980 microns	Thicker paper and slower drainage need a more open bed.
AeroPress	90 to 150 sec	480 to 640 microns	Short steep and press timing between filter coffee and moka fineness.
Espresso	25 to 32 sec	230 to 360 microns	High pressure and short contact time need fine resistance.
Moka pot	120 to 210 sec	420 to 600 microns	Stovetop pressure with less resistance than espresso.
French press	210 to 300 sec	900 to 1150 microns	Immersion extraction where coarse particles reduce sludge.
Cold brew concentrate	12 to 18 hr	950 to 1150 microns	Long cold steeping where coarse grinding limits fines load.

Water temperature is displayed and carried into the guidance table, but it is not part of the micron formula. That separation matters: temperature can change extraction flavor, yet the grind recommendation remains a timing and taste adjustment anchored to the selected brew method.

Worked Examples:

Pour-over drains too fast

A V60 recipe targets 3.0 min but finishes in 2.4 min and tastes sharp. With pour-over selected, actual time entered, and Too sour or sharp chosen, the Grind Guidance table should move toward a finer medium-fine to medium recommendation and describe a tighter dial move.

Espresso runs long and dry

An espresso target is 28 sec, but the shot takes 40 sec and tastes bitter. The timing error and bitter cue both point coarser. The dial suggestion should move upward on a grinder where larger numbers are coarser, but the next real test should still be a modest click change.

Dial range entered backward

If the coarse burr-gap estimate is not above the fine estimate, the dial mapping cannot describe the grinder honestly. Correct the fine and coarse gap fields first, then check the Brew Trace to confirm that the recommended microns, dial adjustment, and current setting agree.

FAQ:

Are microns the same as my grinder dial number?

No. Microns estimate particle or burr-gap size, while a dial number is specific to your grinder. The dial target becomes more useful when you enter your fine stop, coarse stop, and burr-gap estimates.

Why did the recommendation get finer when my target time increased?

Inside each method profile, the slower end of the reference range maps toward the finer edge because finer particles create more resistance and extraction surface. Actual measured time can still push the final result in the other direction.

Should I change water temperature or grind first?

Use grind first when the brew time is clearly off. Temperature is shown as a companion adjustment, usually in small one- or two-degree moves, after timing and grind are close enough to repeat.

Why does the same setting taste different with another coffee?

Roast level, bean density, age, dose, ratio, water, filter, and fines can change extraction even when the dial number is identical. Keep the Brew Trace values consistent when comparing one change at a time.

Glossary:

Micron: A thousandth of a millimeter, used here as an approximate grind-size unit.
Burr gap: The estimated opening between grinder burrs at a fine or coarse reference point.
Drawdown: The time it takes brewed water to pass through a filter coffee bed.
Extraction: The dissolving of coffee compounds into water during contact with the grounds.
Fines: Very small particles that can clog filters, raise bitterness, or add sediment.

References:

SCA Protocols and Best Practices, Specialty Coffee Association.
Golden Cup Standard, Specialty Coffee Association.