Grind Size Chooser

Introduction:

Coffee grind size is the size of the particles left after grinding, and it is one of the main controls behind flow rate and extraction. When the particles are too small, water meets too much resistance and the cup can drift toward bitterness or dryness. When they are too large, water passes too quickly and the brew can taste thin, sharp, or underdeveloped.

This chooser turns that tradeoff into a practical starting point. It uses your brew method, the brew time you want, and optionally the brew time you actually measured to estimate a particle size in microns, label the grind band in plain language, and map that estimate to a grinder dial move when you provide your grinder range.

That makes it useful when you open a new bag, switch from one brewer to another, or try to rescue a cup that missed the mark. A pour-over that ran fast and tastes sour calls for a different response from an espresso shot that dragged and tastes bitter, and the tool keeps those corrections tied to the method you are actually using.

The micron figure should be read as a calibration aid, not as a universal number that transfers perfectly between grinders. Burr geometry, roast level, dose, brew ratio, agitation, filter paper, and water chemistry still shape the result, so the real value of the tool is consistency: it gives you a repeatable baseline for your own setup and helps you move in the right direction with fewer guess-and-check brews.

All calculations stay in the browser, so you can compare scenarios and export the guidance without sending brew data to a server. Treat the recommendation as a dial-in guide that narrows the search space, then confirm it with taste and a measured brew time.

Everyday Use & Decision Guide:

Start with the brew method and the time you want the brew to land. The tool keeps separate timing and micron ranges for pour-over, Chemex, AeroPress, espresso, moka pot, French press, and cold brew concentrate, so the same target time does not produce the same answer across different brewers. A twenty-eight second espresso and a four minute press pot sit in completely different particle ranges, and the presets reflect that.

If you already brewed a cup, add the actual time as well. The chooser compares measured time with target time, then nudges the grind finer when the brew finished too quickly and coarser when it ran too long. That correction is capped so a single extreme brew cannot push the recommendation into unrealistic territory.

The taste check helps with the final adjustment. Sour and weak cups tighten the grind slightly, while bitter, harsh, or dry cups open it up. The water temperature field gives you a place to track your current brew temperature and pairs the result with a reminder that small temperature moves, usually one to two degrees at a time, can support a grind change when the cup tastes unbalanced.

The advanced grinder fields matter when you want the answer translated into your own hardware. By entering the finest and coarsest dial numbers and an estimated burr gap range, you get a dial target and an approximate click move relative to your current setting. That is especially useful when you already know your grinder but want a cleaner, more method-aware way to choose the next adjustment.

In practice, the best rhythm is simple: choose a method, set a realistic target time, brew once, taste carefully, then change one variable at a time. This tool is strongest when it is part of that loop rather than a replacement for it.

Technical Details:

The script normalizes time inputs into seconds, picks the active method preset, and converts the requested brew time into a base particle-size estimate. Each preset stores a target time range, a default target, a micron range, a timing slack window, and a reference water temperature. The base estimate is calculated with a linear interpolation: as the target time moves toward the slow end of the method range, the recommendation moves toward the finer end of the micron range.

If an actual brew time is present, the tool computes the relative error between actual and target time and applies a proportional correction capped at plus or minus 75 percent. Taste feedback is applied after that time correction. The final result is then clamped to a safety envelope that allows some movement outside the preset range without letting the recommendation become absurdly fine or coarse.

Water temperature is not folded into the micron formula itself. The value you enter is displayed in the summary, guidance table, brew trace, and export payload, while the recommendation text uses it as a practical reminder for small follow-up changes. That distinction matters because the tool is primarily a grind selector with taste-aware coaching, not a full extraction model.

The grinder dial target is a separate translation layer. The tool maps the final micron estimate into the burr-gap range you provide, then scales that value across your dial minimum and maximum so it can recommend a click move relative to the current setting. If your grinder calibration is rough, the micron estimate will usually be more trustworthy than the click count.

Assumptions and limitations

• The model assumes grind size is the main correction lever, with taste and temperature used as supporting cues.
• Dose, brew ratio, agitation, filter clogging, roast solubility, and water chemistry are not modeled directly.
• Water temperature is tracked and surfaced in the output, but it does not change the micron formula.
• Cold brew uses very long target times and coarse ranges, so small numeric changes usually matter less than they do in espresso.
• No server processing is involved; the guidance, tables, JSON output, and exports are generated in the browser.

Step-by-Step Guide:

1. Select the brew method that best matches your brewer and style.
2. Enter the brew time you want to hit, using seconds, minutes, or hours as needed.
3. If you already brewed a cup, add the actual time you measured from start to finish.
4. Choose the taste cue that best matches the cup you drank, and confirm your current water temperature.
5. If you want a grinder-specific click move, open the advanced panel and enter your dial range, burr-gap estimates, and current setting.
6. Read the summary first, then use the guidance table, playbook, brew trace, or JSON export to plan the next adjustment.

Interpreting Results:

The headline answer is the grind recommendation itself: a grind band, an estimated particle size in microns, and a grinder-dial suggestion when calibration data is available. That combination tells you both the general direction and the approximate magnitude of the move.

The time window badge shows what counts as close enough for the next brew. It is centered on your chosen target time and widened by a method-specific slack value, so espresso gets a narrow window while long immersion methods get more breathing room.

The taste focus badge summarizes the correction logic in plain language. It does not replace tasting the cup, but it does help you avoid common overcorrections, such as making a sour brew dramatically finer when a small move would be more sensible.

Worked Examples:

A fast, sour pour-over is a good example of the tool at its most useful. With the default pour-over preset, a target of 3.0 minutes and an actual time of 2.5 minutes produce a recommendation of about 565 microns, which lands in the Medium band. Because the cup tastes sour, the guidance also leans toward a slightly finer move and a small temperature increase.

A starting-point cold brew behaves differently. If you choose cold brew concentrate and leave the actual time blank, the tool simply maps the target steep into the coarse preset range. A target near the default 15-hour mark yields a recommendation around the middle of the cold-brew range, which is useful when you want a stable first batch before making smaller texture and extraction adjustments.

The contrast between those examples explains the tool's design: short brews with fast feedback need tighter, more reactive changes, while long immersion brews benefit from a calm starting estimate and slower iteration.

FAQ:

Glossary:

Micron

A micrometre. The tool uses microns as a simple way to express approximate particle-size targets.

Drawdown

The time it takes brewed coffee to pass through the bed and filter. Faster drawdown usually points toward a coarser grind, less resistance, or both.

Extraction

The amount of soluble material pulled from the coffee by water. Grind size, time, temperature, and agitation all influence it.

Burr gap

The space between the grinder burrs. Smaller gaps usually create finer particles.

Fines

Very small particles that can slow flow, raise extraction quickly, and muddy cup clarity.

Immersion brew

A method where coffee spends time steeping in water before separation, such as French press or cold brew.

References:

• Specialty Coffee Association, Certified Home Brewer Program Requirements
• Specialty Coffee Association, How Hot Is Hot Enough? Brew Temperature, Sensory Profile, and Consumer Acceptance of Brewed Coffee
• Specialty Coffee Association, Cold vs. Iced: Using Sensory Analysis to Test the Claim That Cold Brew Is Sweeter and Less Acidic