Building a sphere one layer at a time
A sphere is the hardest round shape to build by eye: every layer is a different circle, and near the top and bottom each ring steps in by several blocks at once while around the middle it barely changes. This page opens on a 21-block sphere with a thick shell, which is 21 layers tall. Set your own diameter and work upward from layer 1.
On a 21-block sphere the first layer is a solid disc 7 blocks across, the shell’s floor. From there the rings widen fast: layer 2 is already 84 blocks. The middle ring, layer 11, spans the full 21 blocks. On each ring, place the four blocks where the dashed centre lines cross it first, then fill the quarters between them.
Where the blocks go
The counts surprise most builders: the middle ring is not the most expensive layer. In a thick shell, layers 5 and 8 take 104 blocks each while layer 11 takes 80, because the sloping parts of the sphere need a wider band of blocks to stay sealed. Layers come in mirrored pairs (1 and 21, 2 and 20, …), so gather materials for both while you are at it, and the PDF prints one page per pair.
Shell or solid?
A solid 21-block sphere takes 4,945 blocks (77 stacks + 17), almost three times the thick shell, and nobody sees the inside. Build a shell unless you are carving a room or a planet’s core out of it later. If the sphere will be a room, the thin shell leaves the most space inside and costs 1,082 blocks.