Abstract: A hopper bottom for a cylindrical grain bin includes a floor structure, an outer cylindrical wall extending up from the floor and upon which the bin is supported, and an inner wall having an inverted cone shape which tapers downwardly and inwardly to join the floor structure about a central area. A pair of spaced apart upright auger chute walls extend radially outward from the central area to an access opening in the outer wall to receive an auger for unloading. Screens are flush mounted in the inner wall such that ventilation air directed into a manifold space between the inner and outer walls is forced up through the screens into the grain bin. The floor structure includes a floor sheet, a perimeter member about the outer wall, and radial supports extending between the central area and the perimeter members.