Portafilter Sizes Explained: How to Measure Yours
To find your portafilter size, measure the inside diameter of the filter basket at its top rim. That number, usually 58, 54, 51 or 49 mm, is what tampers, puck screens, distribution tools and replacement baskets are sized to. Don't measure the outside of the portafilter or the handle: those vary by brand and tell you nothing about which accessories fit.
Below: how to measure correctly, a quick size overview for common machines, and why the half-millimeter between 58 and 58.5 mm matters more than it sounds.
How do I measure my portafilter size?
- Take the basket out of the portafilter if it's removable, or measure it in place.
- Measure the inner diameter at the top rim, straight across the center. A digital caliper gives the most reliable result; a ruler works if you read it carefully at eye level.
- Round to the nearest half-millimeter. A reading of 58.3–58.6 mm means a 58.5 mm "precision" basket; 57.8–58.1 mm means a standard 58 mm basket.
- Check the manual or the basket stamp. Many baskets carry their size or a part number. Use this to confirm your measurement, not replace it.
The size is defined by your machine's group head, so it can't be changed. You can only add a smaller basket (see step-down baskets below), never a bigger one.
What are the common portafilter sizes?
| Size | Typical machines | Notes |
|---|---|---|
| 58 mm | Commercial machines, E61-style home machines, Gaggia Classic, Rancilio Silvia, Breville/Sage Dual Boiler and Oracle | The commercial standard with the widest choice of accessories |
| 58.5 mm | Precision baskets in 58 mm groups, e.g. La Marzocco Linea Micra and Linea Mini R | Same group as 58 mm; the basket wall is slightly wider and straighter |
| 54 mm | Breville/Sage Barista Express, Barista Pro, Bambino | Very common in entry-level home machines |
| 51 mm | Many compact machines, including many De'Longhi models | Check your specific model, sizes vary within brands |
| 49 mm | Step-down baskets for 58 mm groups, some compact machines | Taller, narrower coffee bed, see our 49 mm vs 58 mm basket comparison |
Manufacturers change parts between generations. If your machine isn't listed, or you're unsure, measure.
58 mm vs 58.5 mm: does half a millimeter matter?
Yes, for anything that has to fit snugly against the basket wall.
- Tampers: a 58 mm tamper in a 58.5 mm basket leaves a ring of untamped coffee around the edge, which can encourage water to run down the side. A 58.5 mm tamper in a standard 58 mm basket may not fit at all. Match the tamper to the basket.
- Puck screens: these sit on top of the coffee bed, so a screen sized for the larger diameter covers the whole puck. Our puck screen is 58.5 mm and fits portafilters commonly sold as "58 mm," including the La Marzocco Linea Micra and Linea Mini R.
- Distribution tools: a slightly smaller tool still works; a larger one won't go in.
54 mm vs 58 mm: is bigger better?
Not automatically. A 58 mm basket spreads the same dose into a wider, shallower bed, while 54 mm makes it deeper. Both make excellent espresso. What 58 mm does offer is the widest choice of accessories and baskets, since it's the commercial standard. A 54 mm machine isn't a downgrade, but buy accessories specifically sized for it.
Can I change my portafilter size?
You can't make a group head bigger. You can go smaller with a step-down basket, for example a 49 mm basket in a 58 mm portafilter, which some home baristas use for a deeper bed with lighter roasts. Be aware that a taller basket can reduce the space between the coffee and the shower screen, and some setups lose vertical clearance under the spouts. Our Linea Micra mods guide covers the trade-offs.
What portafilter size doesn't tell you
- Basket depth and dose capacity: two 58 mm baskets can hold 15 g or 22 g. Check the rated dose.
- Ridged vs ridgeless walls: a ridged basket may not let a precision-fit tamper or screen reach the bottom.
- Handle and spout geometry: important for tamper stations and stands, which are designed around a specific portafilter shape rather than its basket size. Our tamper station, for example, is built around 3D scans of the La Marzocco "hybrid" portafilter for the Linea Micra and Mini R, and doesn't fit the classic La Marzocco portafilter.
FAQ
Is a 58 mm puck screen the same as 58.5 mm?
They're sold for the same group heads. A 58.5 mm screen covers the full bed in both standard 58 mm and 58.5 mm precision baskets.
What size is the La Marzocco Linea Micra portafilter?
It uses a 58 mm group with 58.5 mm-class baskets, so 58.5 mm tampers and puck screens are the right match.
How do I measure without a caliper?
Place a ruler across the basket rim at its widest point, read at eye level, and repeat a few times in different directions. Round to the nearest half-millimeter.
Does the outside diameter of the portafilter matter?
Only for stands, tamper stations and knock boxes. For anything that touches the coffee, measure the inside of the basket.
Next steps
Once you know your size, you can match the parts that touch the coffee: start with a 58.5 mm puck screen, and if you're on a Linea Micra or Mini R, a tamper station holds the portafilter level while you tamp. For what a puck screen actually changes, read what does a puck screen do.
