United carry-on baggage should fit in the overhead bins. The maximum dimensions for carry-on baggage are 9 inches x 14 inches x 22 inches (22 cm x 35 cm x 56 cm). Handles and rollers are included.
Personal items should be sized to fit under the seat in the front of the airplane. The maximum size for personal items is 9 inches x 10 inches x 17 inches (22 cm x 25 cm x 43 cm).
Only one personal item may be carried on board if traveling in Basic Economy. If you bring a full-size carry-on bag to the gate, you will need to check a bag.
Expanded Information
The Rules for the International Transportation of Passengers and Baggage on Civil Aviation of China states:
Article 35? The passenger's non-checked baggage shall be handed over to the carrier for counting or counting, and the carrier shall enter the weight and number of pieces into the "passenger ticket and baggage ticket", and the passenger shall take care of himself during the transportation.
The passenger's non-checked baggage brought into the cabin should be able to be placed under the front seat or can be placed in the cabin of the closed storage area. Luggage exceeding the weight or dimensions specified by the Carrier shall not be placed in the passenger cabin.
Article 41? The carrier shall not be liable for any injury to the passenger himself or the loss of his baggage caused by articles in the passenger's baggage. If injury is caused to another person or damage is caused to another person's articles or the carrier's property due to articles contained in the passenger's baggage, the passenger shall compensate the carrier for the loss and the expenses thus paid.
United Airlines website - carry-on baggage