About this tool
This is a block-grid planner for round shapes. You give it a size, it gives you the exact pattern and the exact number of blocks. It covers flat circles and ovals, and it slices spheres and domes into buildable layers. That is the whole scope.
How a circle is decided
One rule: a block belongs to the shape when the centre of that block falls inside the ellipse. There is no anti-aliasing, no partial coverage and no artistic adjustment. It is the same rule the long-standing community pixel-circle generators use, which is why the patterns here match the ones in build tutorials rather than inventing a new dialect.
The comparison is done in doubled integer coordinates instead of floating-point ones. Writing a block's
offset from the centre as 2i - n + 1 makes it an exact integer for both odd and even sizes,
so the "is this inside?" test is exact integer arithmetic. This is not a micro-optimisation — it is
what guarantees symmetry. With floating point, a block sitting exactly on the boundary can round one way
on the left of the circle and the other way on the right, and you get a pattern that is a block out on
one side. That cannot happen here.
The filled style applies that test directly. The outline style keeps only blocks that touch the outside, then drops redundant corner blocks — the ones whose outward neighbour in x and outward neighbour in y are both already on the ring. That is what turns a chunky two-block edge into a clean one-block ring. A five-block circle comes out like this:
.XXX. X...X X...X X...X .XXX.
12 blocks, four-fold symmetric, and connected the whole way round.
What is tested
The rasterizer is a pure library with no browser dependencies, and it ships with an assertion suite that runs on every change. It checks, among other things:
- Exact expected patterns for the small cases — diameters 3, 4, 5, 7 and the well-known 13.
- Mirror symmetry on both axes, and transpose symmetry for squares, across dozens of sizes up to 256.
- That every thin outline is a single connected ring — no gaps to patch, no stranded blocks.
- That the outline is always a subset of the filled disc, and that filled rows never contain holes.
- That sphere layers are symmetric about the equator and that solid layer counts grow toward it.
- That a hollow dome's base course is identical to the flat circle outline of the same diameter.
Every figure in the tables on this site is computed at build time by that same library. Nothing is typed in by hand, so the prose and the tool cannot drift apart.
Honest limits
Where this site quotes a mathematical formula — πd²/4 for area, πd³/6 for volume, √(2d) for the flat run, 2.75 × d for the outline — it is labelled as an estimate and shown next to the exact count, with the size of the gap. Formulas describe smooth curves; block grids are not smooth. The estimates are useful for deciding what to gather; the counts are what will actually be true when you place the last block.
Sphere and dome diameters are capped at 96 in the tool, not because larger ones are wrong but because every layer has to be rasterized to count it, and the slider stops feeling instant beyond that. Flat circles and ovals go to 256 on each axis.
There is also more than one defensible way to rasterize a circle. Algorithms that test corners rather than centres, or that use Bresenham-style midpoint stepping, produce slightly different rings at some diameters. This tool commits to the centre test throughout so that its circles, ovals, sphere slices and dome courses all agree with each other — which is what lets a dome base course land exactly on a tower built from the circle generator.
Privacy, in one line
Everything runs in your browser. There is no account, no upload and no server call — the sizes you type and the PNGs you export never leave your device. The privacy policy has the details, including third-party advertising cookies.
Not affiliated with Mojang
This is an independent fan-made tool. It is not affiliated with, endorsed by, sponsored by or associated with Mojang Studios or Microsoft. "Minecraft" is a trademark of Mojang Studios. Nothing here is an official product, and no game files, assets or account data are involved — the output is a picture of a grid.
Corrections
If a pattern looks wrong, or a count does not match what you built, that is worth reporting — include the exact dimensions and the style you used. The contact page has the address.