How to calibrate a grinder

1. Decide what you are actually fixing

Check the symptom before touching anything. If you can't grind fine enough for espresso, or the dial reads zero while the burrs are still clearly open, the physical calibration may be off. If the grinder works but recipes written for it always come out a little fast or slow, that is a personal offset, and you can skip to step 6.

Baratza suggests trying the simple fix first: if you run out of room at the fine end, a few more grams of coffee may get you there before you recalibrate.

2. Empty the grinder and find the zero point

Grind out any beans, then close the burrs slowly until they just meet. That position is the zero point. Each maker describes it slightly differently:

• Comandante: hold the grinder horizontally. With the burrs open, the handle falls to the 6 o'clock position. Click zero is the first setting, as you tighten, where the handle no longer falls.
• 1Zpresso: turn the adjustment dial counterclockwise until you feel resistance while turning the crank. 1Zpresso stresses that this is not the dial's tightest position.

Don't force the burrs together. 1Zpresso warns against overtightening the dial, which can get the grinder stuck.

3. Check what the dial reads at zero

Look at the dial once you are at the zero point. On a 1Zpresso J-Max, it should read #0 against the scale mark. The J-Max manual describes the check: at the point where the crank can't spin freely, "the #0 will be aligned with the scale mark." On 1Zpresso's internal-adjustment models (Q, J, JX and JE), the starting point doesn't have to be at #0, because the numbers only count how many steps you've turned.

If it reads zero, the grinder is calibrated and you are done with the physical part. If it reads something else, note the difference. Even without adjusting anything, you can count your settings from that true zero.

4. Re-align the dial using the maker's procedure

If the dial is off, follow your grinder's instructions exactly, because the method depends on how it adjusts. 1Zpresso's tutorial gives a separate procedure for each design: internal adjustment (Q and J series), top adjustment (JX-Pro, JE-Plus), external adjustment (K series), and the J-Max and J-Ultra. On the K series, for example, you turn the dial to #0 before installing the inner burr, then secure the thumb nut.

Electric grinders differ again. Baratza says many of its grinders come with calibration tools, and it sells an adjustment kit for the Encore and Virtuoso+. Use Baratza's model-specific calibration guide rather than a general one.

5. Leave factory-set parts alone

Some calibration is done at the factory and isn't meant to be touched. Comandante asks C40 owners not to unscrew the three mounting screws around the burr, which are "carefully and precisely tightened by hand during production to ensure the correct calibration." If a grinder seems badly off after you've checked zero, contact the manufacturer before you take it apart. Uneven burrs are a burr alignment problem, not a dial problem.

6. Calibrate the converter to your unit

Open the grind converter, pick your grinder as the target and start the calibration. You'll need to be signed in to save the result, and saving adds the grinder to your collection. The wizard asks for three reference brews, at grind index 8 (espresso), 38 (pour-over) and 80 (French press), and shows the standard setting for each.

For each one, enter the setting you actually used and say whether the cup tasted too fine, just right or too coarse. "Just right" is taken as the true setting. "Too fine" or "too coarse" nudges it by 3% of the grinder's range or one step, whichever is larger. BrewMark stores the difference from the standard setting at each point and applies it to every later conversion, blending between the three points.

7. Write down your reference points

Record the dial reading at zero and the settings you settled on for each method. If the grinder is ever serviced, recleaned or knocked, checking zero again tells you whether those numbers still hold.

How do you know a grinder needs recalibrating?

The clearest sign is a change you didn't make. If settings that used to work now run noticeably faster or slower with the same coffee and recipe, check the zero point before chasing the recipe. A grinder that won't reach espresso fineness is the other common reason. If you're mostly changing beans, see how to adjust grind for a new bag of coffee first, since a new coffee often explains the difference.

Does calibrating change the grinder's numbers in recipes?

It changes what your numbers mean, not what other people's mean. A recipe written as "20 clicks on a C40" assumes a grinder counted from its true zero. If yours zeroes one click late, you'd need 21 to match. That is also why the grind index treats every conversion as a starting point.