You can carry one personal item, such as a laptop or purse, and a carry-on bag on United Airlines flights from San Francisco to Albany for free. The personal bag must be stored under the airplane seat at your front, so it should be 17 x 10 x 9 inches. The carry-on should measure 22 x 14 x 7 inches, including handles and wheels to fit in the overhead cabin. United has no maximum weight allowance on its carry-on policy.