Portafilter Size Guide
Portafilter size is not really a measurement. It is a fitting, and two machines with the same basket diameter can still need different portafilters.
Measuring gives you half the answer
If you take a ruler to the basket already in your machine you will get a number close to 51, 54 or 58 millimeters, and that number is genuinely useful. It is just not sufficient. The basket sits inside the portafilter; the portafilter locks into the group head with lugs on its outside edge, and those lugs vary in count, in width and in how far apart they sit.
The clearest example is DeLonghi. The Dedica family and the Stilosa family both take a 51 mm basket. A Dedica portafilter has three lugs; a Stilosa portafilter has two. Neither will lock into the other machine. Someone who measures the basket, orders "51 mm" and receives the wrong lug count has done nothing wrong — the number was simply never the whole specification.
The table, by machine
| Machine family | Models | Fit |
|---|---|---|
| Breville / Sage Barista | BES 450, 500, 810, 820, 840, 870, 875, 876, 878, 879, 880, 881 | 54 mm, 3 lugs |
| Breville Barista Max family | Barista Max, Barista Mini, Signature | 58 mm |
| Solis | 1170 | 54 mm, 3 lugs |
| DeLonghi Dedica | EC680, EC685, Dedica Arte EC885 | 51 mm, 3 lugs |
| DeLonghi Stilosa | EC260, ECP3420, EC155, BCO430 | 51 mm, 2 lugs |
| SMEG | ECF01, ECF02 | 51 mm, 3 lugs |
| Severin | KA5995 | 51 mm, 3 lugs |
| Casabrews | 3700 PRO | 51 mm, 3 lugs |
| HiBREW | H7, H7a, H10a | 58 mm |
| Barsetto | Barsetto espresso machines | 58 mm |
How to check the lug count in ten seconds
Take the portafilter out of your machine and turn it upside down. Around the outer rim you will see small tabs sticking out, the pieces that slide into the group head and hold the portafilter under pressure. Count them.
Three lugs means one wide tab and two narrower ones, spaced unevenly so the portafilter only goes in one way. This is the Breville and Sage arrangement at 54 mm, and the DeLonghi Dedica arrangement at 51 mm.
Two lugs means two tabs opposite each other. This is the DeLonghi Stilosa arrangement at 51 mm, and it is also the classic arrangement on larger 58 mm machines.
Once you have the diameter and the lug count, you have the specification. Everything else — handle material, basket capacity, finish — is preference.
What about basket size within the same fit?
Baskets are described by the dose they are designed to hold, usually somewhere between a single shot and a double. A basket that says it takes a double will hold a double comfortably; putting a single dose in it leaves too much headroom, and the puck ends up loose and prone to channeling. Going the other way, overfilling a basket presses the puck against the shower screen and water escapes around the rim instead of through the coffee.
If your shots look wet and cratered when you knock the puck out, and you see spray around the outside edge on a bottomless portafilter, dose down slightly before you change anything else.
A note on 58 mm
58 mm is the most quoted number in espresso and the least specific. It covers a wide range of machines that share a basket diameter and very little else: lug arrangements differ, and so do the depth of the group head and the angle at which the portafilter seats. A 58 mm portafilter built for one machine family will not necessarily lock into another.
The 58 mm fit made here locks into HiBREW H7, H7a and H10a, the Breville Barista Max, Mini and Signature, and Barsetto machines. If your 58 mm machine is not one of those, tell us the model before ordering and we will say plainly whether it matches.
If your model is not listed
Measuring is the fallback, and it works as long as you measure the right thing. Take the basket out of your portafilter and measure the outside diameter of the basket rim, not the inside of the portafilter and not the group head. You will land within a millimeter or so of 51, 54 or 58. Round to the nearest of those three: manufacturers describe the same basket as 53 mm, 53.3 mm or 54 mm depending on where they measured it, and they all take the same part.
Then count the lugs, because that is the half of the specification a ruler cannot give you. With the diameter and the lug count together you can compare against the table above and see which family your machine belongs to, even if the model itself is not named.
One thing a measurement will not tell you is group depth. Two machines can share a diameter and a lug count and still seat the portafilter at slightly different heights, which shows up as a handle that locks much further round than expected. It is rarely a problem in practice, but it is the reason we ask for the model number rather than a measurement when there is any doubt.
Basket depth, dose and why they interact
Diameter gets all the attention, but depth is what decides the dose. A 51 mm basket is shallower than a 58 mm one, and it is designed around a smaller quantity of coffee. Filling any basket to the same visual level you used on a different machine is how people end up systematically over- or under-dosing.
The symptom of overdosing is a puck pressed hard against the shower screen. You will see a clean circular imprint of the screen on the surface of the puck when you knock it out, and on a bottomless portafilter you will see water escaping around the outside rim rather than through the coffee. The symptom of underdosing is the opposite: a loose, wet puck that breaks up when you tip it out, and a shot that runs fast and pale.
Weighing the dose once, writing the number down, and using it every time removes both problems permanently. It is the single change that makes the most difference to how a bottomless portafilter behaves, and it costs nothing.
Still not sure?
Send us the model number printed on your machine. That is faster and more reliable than a measurement, and it is the same check we would run ourselves. The Breville page and the DeLonghi page go into each family in more detail, and the main page carries the full fit table.
Sizing questions
How do I know what size portafilter I need?
Look up your machine model rather than measuring. The model number is printed on a label underneath or on the back of the machine. Diameter alone is not enough, because 51 mm exists with both two and three lugs and the two do not interchange.
Are all 58 mm portafilters the same?
No. 58 mm describes the basket diameter, not the fitting. Lug arrangement, group depth and seating angle vary between machine families, so a 58 mm portafilter made for one machine will not necessarily lock into another.
What is the difference between 51 mm two-ear and three-ear?
The number of tabs on the portafilter rim that lock into the group head. DeLonghi Dedica machines use three; DeLonghi Stilosa machines use two. Both take a 51 mm basket, and neither portafilter fits the other machine.
Can I use a bigger basket in the same portafilter?
Within the same diameter, usually yes, as long as the basket seats flat on the rim. What matters more is matching the dose to the basket: a basket run well under its intended dose leaves the puck loose, which is one of the common causes of channeling.