Compare our cabin case to another brand's and ours will often look larger on paper. It usually is not. We are measuring a different thing.
Every dimension on this site is the case overall — wheels included, handle housing included. It is the number you would get holding a tape measure against the finished object.
A lot of luggage is listed body-only: the shell, without the wheels underneath it or the handle on the back. That can be several centimetres of difference on a cabin case, and it is several centimetres in the direction that matters, because the wheels sit on the longest axis.
Why it matters at the gate
Airline sizers do not care where the shell ends. The case goes into the frame with its wheels on, or it does not go in. A case listed at 55cm body-only can be 58 or 59cm in the sizer, and the person holding it has done nothing wrong — they read the number they were given.
So the honest number is the overall one, even though it makes our cases look bigger next to a competitor measuring differently. If you are comparing two cases and one looks suspiciously compact for its capacity, it is worth checking which of the two things is being measured.
What to do with it
Take the overall figure from our page, find your airline's cabin allowance for the fare you actually booked — not the airline's headline number, which often applies to a fare you did not buy — and compare the two. That is the whole method. We would rather hand you both numbers than tell you it fits.
Our Airline Cabin Guide goes through this in more detail, including why we do not publish a table of carriers: allowances change, and a table that is right today becomes a promise that is wrong in a year.