Portafilter Sizes Explained: 51mm vs 54mm vs 58mm

Accessories are sold by diameter, not by machine. A basket, a tamper, a distribution tool, a WDT funnel and a bottomless portafilter all describe themselves in millimetres, and a listing that says "fits Breville" is really saying "54mm". Once you know your number, the whole accessory market becomes shoppable; until you do, you are guessing from brand names.

It also travels with you. If you upgrade machines later, staying within the same diameter means your tamper, baskets and funnel all move across. Changing diameter means replacing the lot — which is a quiet argument in favour of 58mm that we will come back to.

58mm is the commercial standard. It is what café machines use, which means it is the size with the deepest catalogue of baskets, tampers, distribution tools and precision parts. If you buy a 58mm machine, you are buying into an accessory market built for professionals.

54mm is Breville's size, across the whole range.Because Breville sells in such volume, 54mm has a genuinely healthy aftermarket of its own — not as deep as 58mm, but far better served than anything else outside the commercial standard.

51mm is the smallest of the three, used by De'Longhi's manual machines. Its aftermarket is real but thin, and its baskets hold less, which caps the dose you can work with.

The De'Longhi pattern is worth memorising because the model numbers encode it: an EC prefix is a manual machine with a 51mm portafilter, while ECAM and EXAM are bean-to-cup machines with no portafilter at all. Our De'Longhi lineup decoder works through the rest of the naming, and the Breville equivalent does the same for the 54mm range.

If your machine is not in the table above, measure it. There is one right way and one common wrong way.

1. Take the basket out of the portafilter. The basket is the removable perforated cup that holds the coffee.
2. Measure across the widest part of the basket's top rim, outside edge to outside edge. That is your size. It will land within a millimetre of 51, 54 or 58.
3. Round to the nearest standard size.Manufacturing tolerance means you may read 53.8mm or 58.2mm. There is no 53mm or 57mm portafilter standard — you have a 54mm or a 58mm machine.

The wrong way is measuring the outside of the portafilter body, which includes the metal rim and the lugs that lock it into the group head. That number is always larger than the size you need to shop with, and it is how people end up ordering 58mm parts for a 54mm machine.

Failing all that, the model number is the fastest route: search your exact model — BES870XL, EC260, and so on — rather than the family name, because brands reuse family names across different sizes.

This confuses almost everybody the first time. A tamper has to fit insidethe basket, and a basket's inner diameter is slightly larger than the nominal portafilter size. So tampers are sold marginally over the headline number: 58.5mm for a 58mm machine, and typically a similar fraction over for 54mm.

The reason a close fit matters is mechanical, not cosmetic. A tamper appreciably narrower than the basket leaves an unpressed ring of coffee around the edge, and water takes the easiest path — straight down that ring. That is channeling, and it is the most common cause of a sour, thin shot. A tamper sized correctly presses the whole bed evenly.

The corollary: do not buy the "fits all" tamper that shipped in the box with many machines. It is usually plastic and usually undersized. Our tamper and puck prep guide covers what a correctly sized one changes.

It is tempting to read 58mm as "better". It is more accurate to say it is better supported, and slightly more forgiving.

• A wider, shallower puck. The same dose spread over more area makes a shallower coffee bed, which is marginally more tolerant of a slightly uneven tamp. A 51mm basket concentrates the same coffee into a deeper column, where a flaw has more depth to travel through.
• More headroom on dose. 58mm baskets are available in a far wider range of capacities, so you can run larger doses if you want to. 51mm baskets are small, and that is a hard ceiling.
• The full professional accessory catalogue.Precision baskets, distribution tools, funnels, puck screens — the interesting parts of the accessory market are built for 58mm first and everything else second.
• Upgrade continuity. If you expect to move up to a prosumer machine eventually, buying 58mm now means your tamper, baskets and tools survive the move.

What a bigger portafilter does notbuy is a better shot on its own. A well-dialed 54mm Breville beats a badly dialed 58mm machine every time, and the grinder matters more than either — which is the argument in do you need a grinder for espresso.

• "Fits Breville" does not mean fits every Breville. All Breville espresso machines are 54mm, but portafilter handles and lugs vary enough between the Bambino line and the Barista line that some third-party 54mm portafilters list compatibility for one and not the other. Read the model list, not just the diameter.
• Gaggia is 58mm, Breville is 54mm. These are the two most common home machines on this site and they share nothing. A 58mm basket will not sit in a Breville and a 54mm tamper is useless in a Gaggia.
• Bean-to-cup machines take none of it.If your De'Longhi model number starts ECAM or EXAM, there is no portafilter to upgrade.
• Tamper numbers are not portafilter numbers. 58.5mm is the tamper for a 58mm machine, not a different machine standard.
• Manual presses are their own world. Flair and Wacaco use 40mm, 49mm and 52mm depending on model, and those accessories come from the manufacturer rather than the general market. See best manual espresso machines.

With the number settled, the first upgrade worth making is a bottomless (naked) portafilter in your size. It is the cheapest diagnostic tool in espresso: it does not improve the shot, it shows you exactly where the shot is going wrong, by letting you watch the extraction directly rather than through a spout. The second is a tamper that actually fits.

If you have a 54mm Breville. Two good options, and the difference is fitment breadth. The wider-fitment version lists the Bambino Plus alongside the Barista models, which matters if you own more than one machine or expect to change within the Breville range; the value version covers the Barista line for less.

If you have a 58mm machine. The general-fit option ships with a double-shot basket and a wooden handle, which makes it a complete swap rather than a body you still need to find a basket for. If you specifically own a Gaggia Classic Pro, Evo or E24, the KNODOS unit is built around that fitment.

And the tamper, at 58.5mm for a 58mm machine. This is the part that stops the edge channeling a bottomless portafilter will immediately show you.

Prices shown are from Amazon as of Sep 18, 2026 and change often — the button always goes to the current listing. Some links may earn us a commission at no extra cost to you.

One thing to know before you fit a bottomless portafilter: it will also make it obvious whether your machine is using a pressurized (dual-wall) basket, which hides almost everything a naked portafilter is meant to reveal. Our pressurized vs non-pressurized guide explains the difference and what you need before switching. Our best bottomless portafilters roundup goes deeper on reading the spray pattern once you have one.