The following United Airlines baggage policies are for passengers traveling in economy class, and are not top tier frequent flyer members (Premier Associate status or higher in Mileage Plus or Silver status and above with a Star Alliance partner are exempt from this policy) for flights within the United States, the US Virgin Islands, Puerto Rico and Canada:
Baggage Allowance - Your first checked in bag is $25, your second is $35, with a weight allowance of 50lbs (23kg) per bag, and an additional 40lbs maximum of carry on luggage.
For Europe, Mexico and the Caribbean - 1st bag free then
$50 for second bags on flights to Europe, and $30 for 2nd checked pieces for the Caribbean and Mexico.
Other international destinations permit 2 bags weighing a maximum of 50lbs each for free (except Brazil which allows for a maximum of 70lbs each).
Excess baggage fees for extra/oversized/overweight luggage start at $125 and can run up to several hundred dollars. If it weighs over 100lbs it will not be accepted and you will need to contact cargo for freight charges.
United Airlines policies regarding checking strollers, car seats, mobility devices and sports equipment.