Minecraft
Circle, Sphere & Dome Generator
Building a round tower, a dome or a planet by counting blocks on graph paper takes an evening and still ends up lopsided. Enter the size and this lays the shape out block by block, one layer at a time, with a row-by-row list you can follow while building.
Thin outlines touch only at corners and use the fewest blocks. Thick outlines have no diagonal gaps, so nothing can slip through.
- Blocks
- 80
- Blocks in total
- 80
- 1 stacks + 16
Each square is one block. The lines mark the centre.
Row by row
Each row, top to bottom: which columns get a block, counted from the left edge starting at 1.
1: 8-14 2: 6-8, 14-16 3: 5-6, 16-17 4: 4-5, 17-18 5: 3-4, 18-19 6: 2-3, 19-20 7: 2, 20 8: 1-2, 20-21 9: 1, 21 10: 1, 21 11: 1, 21 12: 1, 21 13: 1, 21 14: 1-2, 20-21 15: 2, 20 16: 2-3, 19-20 17: 3-4, 18-19 18: 4-5, 17-18 19: 5-6, 16-17 20: 6-8, 14-16 21: 8-14
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How it works
A block belongs to the shape when its centre lies inside the circle, ellipse or sphere of the size you asked for. That makes the result exactly as wide as requested, for even sizes as well as odd ones — an even-width circle has no single middle block, which is simply how the grid works. Outlines keep only the blocks on the edge: thin outlines test the four neighbours on each side, thick ones test all eight, and hollow spheres test the six faces around each block.
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Common mistakes
Pick the outline style for the job. A thin circle uses the fewest blocks but its edge only touches at the corners, so light, water and mobs get through the diagonal gaps; walls and anything meant to keep things in want the thick style. For a dome, the height is how tall it stands: set it to half the width for a true hemisphere.