What are the dimensions of NFL goal posts?

Per the NFL rule book, the goal posts must be 18 feet 6 inches apart and extend vertically at least 30 feet above the cross bar. The top face of the cross bar must be exactly 10 feet above ground. The goal posts must be painted bright gold with a ribbon 4 inches wide and 42 inches long attached to the top of each.

The goal posts used to be placed right at the goal line; however, the NFL elected to move them to the back of the end zone in 1974 as a safety precaution since they often interfered with play.