Here's the annoying truth about Canadian carry-ons: a bag can be "Air Canada approved" and still get stopped at a WestJet gate. The fix is one size. A carry-on of 55 × 36 × 23 cm or smaller, wheels and handles included, fits both airlines.
Air Canada allows 55 × 40 × 23 cm; WestJet allows 56 × 36 × 23 cm. So your bag needs Air Canada's shorter length and WestJet's narrower width. Most bags sold as "Air Canada size" are a few centimetres too wide for WestJet, and that's exactly where people get caught.
Ignore the inches on the label
A "22-inch carry-on" sounds right until you do the maths: 22 inches is about 56 cm, already over Air Canada's 55 cm before anyone measures the wheels. Brands love to leave wheels and handles out of the size. Airlines don't. Get the tape measure out, or use the size finder below to work out the biggest bag that fits every airline on your trip.
For most people flying Air Canada and WestJet, a hard-shell carry-on at the size above is the easy answer. Hard shells hold their shape when packed full, so they don't quietly bulge past the limit the way a stuffed soft bag does.
Connecting through Doha, Dubai or Amsterdam?
The Gulf and European airlines are stricter, and some of them actually weigh your bag. To fit every airline we track, go down to 50 × 35 × 22 cm and keep it under 7 kg packed. That's where a lightweight compact carry-on earns its keep: when the bag itself is light, more of that limit is left for your clothes.
On a Basic fare, the personal item is the whole game
Basic and UltraBasic fares often include only a bag that fits under the seat, and turning up at the gate with a full carry-on costs you. A personal-item bag of 40 × 30 × 14 cm or smaller fits under the seat on every airline that publishes a size. Pick one with a trolley sleeve so it rides on your suitcase handle through the terminal.
Three small things that help more than they should
Compression packing cubes squeeze a week of clothes into a carry-on and keep everything tidy when security opens your bag. A digital luggage scale saves you from the 23 kg surprise at check-in, especially on the way home with gifts. And a luggage tracker in your checked bag tells you where it is when the airline isn't sure.