How to use it
- Look at the bottom layer in the tool, then use Next to move up.
- Build each layer completely before starting the next one.
- Use the faint outline of the layer below as your guide.
- Stop at layer 21. The layers above the middle mirror the ones below it.
The 21 block sphere in numbers
Twenty one blocks is a classic: tall enough for three floors, small enough to finish in one evening. It is a good size for a bubble house, a giant ball or a big tree crown.
The solid version holds 4,945 blocks. The ideal volume of a ball this wide is about 4,849, so the blocky version is 2 per cent larger. The hollow shell is 22 per cent of the solid count, which is why almost every sphere you see in a build is hollow.
| Style | Blocks | Stacks of 64 |
|---|---|---|
| Hollow, thin shell | 1,082 | 16 stacks + 58 |
| Hollow, thick shell | 1,850 | 28 stacks + 58 |
| Solid | 4,945 | 77 stacks + 17 |
Blocks in every layer
The table lists the first 11 layers from the bottom. The top half is the same list in reverse. The widest layer, the equator, has 349 blocks when solid and 56 when hollow.
| Layer | Solid | Hollow |
|---|---|---|
| 1 | 37 | 37 |
| 2 | 97 | 60 |
| 3 | 145 | 48 |
| 4 | 193 | 48 |
| 5 | 241 | 48 |
| 6 | 277 | 52 |
| 7 | 293 | 52 |
| 8 | 325 | 56 |
| 9 | 341 | 56 |
| 10 | 349 | 56 |
| 11 | 349 | 56 |
Centre and equator
With an odd diameter the sphere has one centre block and one equator layer, layer 11. A pillar of 21 blocks through the centre lets you mark every layer. The bottom layer is a small disc of 37 blocks, and the radius grows quickly in the first few layers, then slowly near the middle.
How to build it
Work from the bottom up. Finish each layer, then check it against the faint outline of the one below. For hollow spheres, leave the inside empty and fill only the first layer if you want a floor. Mark the layer numbers on a pillar or a sign so you never lose your place. In survival, collect 16 stacks + 58 for the thin shell, and a few extra stacks of scaffolding or dirt for placing blocks in the air.
Compared with nearby sizes
A small change in diameter changes the cost a lot, because the shell grows with the square of the width. Here is the 21 block sphere next to its neighbours in this guide.
| Diameter | Hollow | Solid | Chests for hollow |
|---|---|---|---|
| 15 | 530 | 1,791 | 1 |
| 21 (this page) | 1,082 | 4,945 | 1 |
| 31 | 2,382 | 15,515 | 2 |
Chests are single chests with 27 slots, full of stacks of 64. The hollow 21 block sphere fills 1 of them. A solid one fills 3. If that is more than you want to gather, drop to a smaller diameter or keep the sphere hollow and use the thin shell.
Other sphere sizes
For ellipsoids or sizes not listed, use the sphere generator. For half a sphere, see the dome generator, and use the stack calculator to plan chests.
Height limit information is from the Minecraft Wiki, checked on 25 October 2026. BlockShapes is not affiliated with Mojang or Microsoft.
Frequently asked questions
How many blocks is a 21 block sphere?
A solid sphere needs 4,945 blocks, which is 77 stacks + 17. A hollow one with a thin shell needs 1,082 (16 stacks + 58), and a thick hollow shell needs 1,850.
How many layers does a 21 block sphere have?
21 layers, one for each block of height. The widest layer is the equator with 349 blocks when solid.
Is a hollow 21 block sphere closed?
Yes. The thin shell keeps every block that touches empty space on a face, so it has no holes you could walk through. Corners may touch only at their edges, so choose the thick shell if you need a shell with no diagonal gaps.
Does 21 blocks fit under the build limit?
Yes. The Overworld in Java Edition 1.18 and later is 384 blocks tall, so a sphere of 21 blocks uses 5 per cent of the height.
Which is better, 15 or 21?
A sphere of 15 needs 530 blocks hollow, 552 fewer than 21. A sphere of 31 needs 2,382 blocks hollow, 1,300 more. Choose by the space you have and the material you can gather.