Minecraft wiki entry for Iron_golem_farming, associated text: The maximum number of spawnable blocks in a farm is 512. This is achieved by two minimum 16×16 solid block platforms centered horizontally at the village center, with one platform four blocks under the village center, and the other platform a block above the village center. In farms designed for maximum rates, the beds are usually arranged tightly around the horizontal center on the Y-level just below the upper spawn platform. This allows iron golems to be transported underneath the beds and ensures that the Y-level of the center does not shift. With 512 spawnable blocks, 98.3% of spawn attempts can succeed.