Why doesn't a circle of diameter 17 look like 17 blocks wide?

It measures 17 blocks at its widest point, but the shape is approximated on a square grid, so the rows at the top and bottom are shorter. The widest row has 17 blocks; the top and bottom rows of a hollow circle have 5. That stair-stepping is normal pixelisation, not an error.

Should I build an odd or even diameter?

Odd diameters have a single centre block, which makes it easy to measure from the middle outward in all four directions. Even diameters sit on a block boundary instead, with no single centre block. Both are symmetrical; pick odd if you want an obvious centre, even if you are aligning to an existing even-width structure.

How many blocks do I need for a hollow circle?

A hollow ring uses far fewer blocks than a solid disc: diameter 17 needs 48 wall blocks instead of 225, and diameter 33 needs 92 instead of 861. The generator shows both counts so you can size your material list before you start.

Is this the same as the Plotz circle generator?

It uses the same underlying idea: test each grid square against the radius and draw the squares that fall inside. Different generators can differ by a block or two because of how they round the radius, so compare the layout before committing to a large build.

Can I use this for a sphere or a dome?

This tool generates a flat 2D circle. A sphere or dome needs a circle of a different diameter on every layer, which is a separate calculation. Build the flat circle first, then shrink the diameter as you go up.

Minecraft Circle Generator — Block-by-Block Layout

Why you need a generator at all

A circle in Minecraft is a compromise. The world is made of cubes, so a "circle" is really a staircase of blocks that reads as round when you stand back from it. You can eyeball it — most builders do — but the results wobble, and a wobble that is three blocks off is very hard to fix later in a wall that is 40 blocks across.

The fix is to decide the shape on paper first. A generator does that by testing every square of a grid against the radius: if the centre of the square is inside the circle, the square gets a block. That is the whole algorithm, and it is why the output is symmetrical by construction rather than by your patience.

How the numbers behave

Two things surprise people the first time they use one of these tools.

The diameter is the widest point, not the width of every row. A diameter-17 circle has one row of 17 blocks, but its top and bottom rows are much shorter — the outline is a staircase. That is not a bug and it is not avoidable; it is what a circle looks like when its pixels are one metre across.

Hollow is dramatically cheaper than solid. The area of a disc grows with the square of the radius, but the circumference only grows linearly. Going from diameter 17 to diameter 33 multiplies the solid block count by nearly four (225 → 861) while the hollow ring goes up by less than double (48 → 92). If you are building a tower floor or a decorative outline, hollow is almost always what you actually need.

Block counts for common diameters

Diameter	Solid disc	Hollow ring
5	21	12
9	69	24
13	137	36
17	225	48
21	349	56
25	489	68
33	861	92
49	1,877	132
65	3,313	180

Counts are for the grid this generator produces. Another tool may differ by a block or two because of how it rounds the radius — if you are matching an existing build, check the outline rather than the total.

Building it without losing the shape

Mark the centre first. An odd diameter has one centre block; an even diameter has a 2×2 centre. Everything is measured from there, and every mistake later is easier to see against a correct centre.
Build one quadrant, then mirror it twice. The pattern is symmetric left-right and top-bottom, so you only ever have to get a quarter right. This is also the fastest way to catch a mis-placed block — the mirror will show it immediately.
Lay the outline before filling. If you are making a solid floor, the outline is the part that has to be right; the interior is just fill. Doing it the other way round means demolishing solid work to fix a curve.
Check at eye level, not from above. From directly overhead a slight stair-step looks wrong; from the ground it disappears. Judge the curve the way players will see it.

What this tool does not do

No spheres or domes. This is a flat, two-dimensional circle. A dome is a stack of circles of decreasing diameter, one per layer — same principle, different calculation.
No material or colour planning. It tells you how many blocks, not which ones.
No guarantee of matching another generator. Pixel circles are not unique: a different rounding rule produces a slightly different staircase for the same diameter.

Nothing here is game data, so it does not go stale with a version update: it is geometry, and it applies to any version of the game — or to any other block-building game with a square grid.

Frequently asked questions

Why doesn't a diameter-17 circle look 17 blocks wide?

It is 17 blocks at its widest row only. The rows near the top and bottom are progressively shorter, because the outline follows the curve rather than the bounding box. A hollow diameter-17 circle has just five blocks in its top row.

Odd or even diameter — which should I pick?

Odd gives you a single centre block, which makes measuring outwards easy and makes the symmetry visually obvious. Even sits on a block boundary with a 2×2 centre and no single middle block. Use even when you are fitting the circle into a structure that is already an even number of blocks wide.

How many blocks for a hollow circle?

Far fewer than solid: 48 versus 225 at diameter 17, and 92 versus 861 at diameter 33. Both counts are shown above as soon as you enter a diameter, so you can size the build against what you have in storage.

Is this the same as other circle generators?

The idea is the same everywhere — test each square against the radius — but the rounding differs, so the exact stairs can shift by a block. If you are continuing someone else's build, match the existing outline rather than trusting any single tool.

Can I make a sphere with this?

Not directly. A sphere needs a different diameter on each layer. Build the flat circle at the full diameter for the equator, then reduce the diameter as you go up or down — one circle per layer.

Method

Each square in an n×n grid is tested at its centre point against a radius of n/2. Squares whose centre falls inside the circle are drawn; hollow mode then keeps only the drawn squares that touch an empty square or the edge of the grid. The result is symmetric on both axes for every diameter from 1 to 64, which is why you can safely build one quadrant and mirror it.