As of June 2015, the general dimensions for carry-on luggage are 22 inches high, 14 inches wide and 9 inches deep. There is not a set weight limit that the bag must not exceed, but passengers need to lift the bags into the overhead bin on the airplane.
According to the Federal Aviation Administration, the linear size of a carry-on bag cannot exceed 45 inches. Linear size is the total of the three dimensions of a bag, including the height, width and depth. Each airline provides its own dimensions within this 45-inch linear limit, and individual airlines provide that information to passengers upon request or on their websites.