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espressosizes

Sizes

How to measure a filter basket, tamper and portafilter

Start with the manufacturer's figures for your machine: the checker lists them with their sources. Measure your own parts when you have a basket or tamper of unknown origin, when you are checking a used machine, or when the manufacturer does not publish the size you need.

What you need

Digital calipers. Neighboring portafilter sizes differ by only a few millimeters, and a tamper has to fit a basket more closely than that, so a ruler cannot tell you what will fit. Clean the parts first: dried coffee oils on a basket wall are enough to throw off a reading.

Nominal size and measured size are different things

The portafilter size a manufacturer quotes is a nominal size. It names the group and the family of baskets that fit it, and it is not necessarily the measurement of any one surface you can put calipers on. Two numbers matter more when you buy accessories: the basket's inner diameter, which decides the tamper and distribution tool, and the basket's outer rim, which decides whether a basket sits in a portafilter at all.

Filter basket: inner diameter

  1. Take the basket out of the portafilter and wipe the inside of the rim.
  2. Put the calipers' inside jaws just below the lip and open them until both touch the wall.
  3. Turn the basket a quarter turn and measure again. Pressed baskets are rarely perfectly round; use the smaller of the two readings.
  4. Measure again about where the top of the coffee bed sits after tamping. Many baskets narrow slightly toward the base, and the tamper has to fit at that depth, not only at the lip.

Tamper: base diameter

Close the outside jaws across the widest part of the base, then turn the tamper and measure again. The base must be smaller than the basket's inner diameter at the depth you measured in step 4. If it is as wide as the basket it will not go in; if it is much narrower, it leaves a ring of loose coffee around the edge that water can run through. Distribution tools follow the same rule.

Pressurized or not

Turn the basket over. A single-wall (non-pressurized) basket shows holes across the whole base. A dual-wall (pressurized) basket has a second, solid outer wall with one small exit hole. Many machines ship with both kinds, so check each basket you have.

Portafilter

A portafilter is specific to its group. Diameter alone does not guarantee a fit: the locking lugs, their spacing and the angle at which they engage have to match the group head as well. Use the nominal size to rule out the wrong portafilters, then buy one that is listed for your machine model. Abottomless portafilter follows the same rule and takes single-wall baskets.

Group gasket and shower screen

For a replacement gasket, the outer diameter, inner diameter and thickness all matter. Measure the old gasket only as a check: gaskets flatten and harden in use, so an old one reads thinner than a new part. The manufacturer's part number, where it publishes one, is the safer guide. Shower screens are sized by their outer diameter, measured across the flat face.

Reading the result

Compare your readings with the figures on your machine's page. If a reading falls between two published sizes, measure again at a right angle to the first and go by the manufacturer's figure for your model. Where a manufacturer does not publish a size, this site says so rather than giving an estimate.

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