International carry-on sizes are often slightly smaller than U.S. sizes, and weight limits are enforced much more strictly.
U.S. standard: 22 x 14 x 9 inches, no weight limit on most full-service carriers.
International standard: roughly 22 x 15 x 9 inches (55 x 40 x 23 cm), with a 7 kg (about 15 pound) weight limit on many European, Asian, and Middle Eastern airlines.
The practical impact: a bag that passes in the U.S. can fail internationally because:
- Budget airlines in Europe and Asia measure in metric and enforce every millimeter
- Economy fares on international carriers often cap carry-ons at 7 kg including the empty bag weight
- Some airlines accept only 8 inches depth instead of 9
For flights that mix both, target a bag that measures 21 x 14 x 9 inches and keep it under 15 pounds packed.
See: carry-on size limits by airline and the luggage calculator.