What size bag should you buy?
The single bag size that fits every reviewed airline in each group — calculated from published limits and explained with the trade-offs left by the strictest carrier.
Sizes shown as largest × middle × shortest side (orientation doesn’t matter for the sizer).
Each guide takes a group of airlines and finds the single largest bag that still fits every one of them for free. The strictest carrier in the group sets the limit on each side, so buying to that size clears the whole group — go bigger and you are gambling on the tightest airline. Pick the group that matches how you travel and buy once.
Choosing one bag size — FAQ
How is the “best size” calculated?+
For each side we take the smallest limit across every airline in the group, so the resulting box fits all of them. It is the element-wise minimum of the published limits — the strictest carrier sets each dimension.
Why is the recommended size smaller than some airlines allow?+
Because it has to clear the strictest airline in the group. A bigger bag might fit most of them and still fail the tightest one, which is exactly the case that gets bags gate-checked. Buying to the shared size removes that risk.
Do these sizes include wheels and handles?+
Yes. Like every size on the site, the figure is the outside measurement of the packed bag, including wheels, handles and bulging pockets.
What if I only ever fly one airline?+
Then you do not need a shared size — open that airline’s own guide and buy to the largest bag it accepts for free. The best-size guides are for travellers who mix carriers across a trip or a year.