The method
Where every number on this site comes from
A dimension is only useful if you know how it was taken. This page is the whole method, written down once, so that any figure you see anywhere on the site can be checked against it.
We compare numbers, not policies. Airlines change limits and measure differently at the gate.
The outline
Length and height are read across the dashed outline. Depth is read the same way, at the widest point of the loaded body.
01Six rules
What we do every time
- 01
Bounding box, not body
A bag is measured across the outline that contains all of it. Handles, feet, buckles, straps in their stowed position and any projecting hardware are inside the figure. We do not publish a body-only number and leave you to add the rest at the gate.
- 02
Laid flat, empty, unexpanded
The first figure is taken with the bag empty, laid flat on a level surface, every expansion zip closed, every compression strap released and nothing clipped to the outside. This is the baseline and it appears on every product page.
- 03
Expanded, where an expansion exists
If a piece has an expansion gusset or a compression system, the second figure is the same bag at its other setting. Both numbers are published, because the one that matters is whichever setting you are actually carrying.
- 04
Loaded, with the contents listed
A loaded figure is only published alongside the list of what was inside. Without the list the number means nothing, so where no list exists, no loaded figure is shown at all.
- 05
Rounded up, never down
Every measurement is taken three times and the largest result is published, rounded up to the nearest whole centimetre. Where we are uncertain, the number moves against us.
- 06
Softness is published too
How much a bag gives back under pressure changes what happens at a fixed opening. Each piece carries a build rating and the approximate give that goes with it.
02Worked example
Underseat Expand, all three states
The same bag, measured at each of its settings. Note that the loaded figure is larger than the expanded one — fabric under load does not sit perfectly flat, and we publish what the tape reads rather than what the pattern says.
Empty, unexpanded
40 × 25 × 18 cm
Empty, expanded
40 × 25 × 24 cm
Filled, as listed
40 × 26 × 25 cm
Loaded with
- 2 hooded sweatshirts
- 4 T-shirts
- 2 pairs of trousers
- 1 toiletry pouch
- 1 pair of shoes
03Build
Give under pressure is a measurement
Two bags with identical published figures will behave differently at a fixed opening. The one with no frame will lose several centimetres; the one with a moulded base will lose none.
Fully soft
gives up to 4 cm
No frame anywhere. Pushed against a fixed opening it will lose up to four centimetres, and it will not hold its shape while you load it.
Semi-structured
gives up to 2 cm
Stiffened panels in the sides. It stands up on its own and still gives roughly two centimetres under steady pressure.
Structured base
gives up to 0 cm
A moulded base and framed opening. Easy to pack, and it gives nothing back. The published figure is the figure.
What this method does not do
None of the above tells you whether a piece will be accepted as cabin baggage. We have no visibility of the rules on your ticket, the aircraft you board or the equipment used at your gate, and we make no claim about any of them. Our commitment is narrower and, we think, more useful: the numbers we publish are the numbers we measured.