Minecraft Coordinates Calculator: Chunk, Region, Slime Chunk
An all-in-one Minecraft coordinates calculator. Convert blocks to chunks and regions, check slime chunks by seed and convert Nether coordinates. Four tools in one, completely free and with no sign-up.
Enter block coordinates (X, Z) and the calculator works out which chunk and region you are in. It also gives the region file name (.mca), which is handy when editing a world.
r.0.0.mca.mca files store the world's chunks on disk. Each region file holds 32x32 chunks (512x512 blocks). You need it when deleting problem chunks, moving parts of a map between worlds or debugging terrain generation errors. Region files live in the region folder of each dimension in your world save.
The Minecraft coordinate system
Minecraft uses a three-dimensional Cartesian coordinate system. Every block in the world has a unique position described by three numbers:
- X - the east-west axis. Positive values go east, negative values go west.
- Y - the vertical axis. From Y=-64 (bedrock) to Y=320 (the build limit). Sea level is Y=63.
- Z - the north-south axis. Positive values go south, negative values go north.
To check your coordinates, press F3 (Java Edition) and look for the "XYZ" line on the debug screen. In Bedrock Edition, turn on "Show Coordinates" in the world settings.
Minecraft organizes the world in a hierarchy: blocks → chunks → regions. Understanding this structure is key to advanced mechanics such as farms, optimization and world editing.
What is a chunk?
A chunk is a 16x16 column of blocks that extends the full height of the world (from Y=-64 to Y=320). It is the basic unit in which the world is loaded: Minecraft doesn't load individual blocks, it loads whole chunks at once. When you approach a new area, the game loads the chunks around you. When you move away, chunks are unloaded from memory.
Every chunk has (X, Z) coordinates, which you get by dividing the block coordinates by 16
and rounding down: chunkX = floor(blockX / 16). For example:
- Block X=50 → chunk X=3 (50 / 16 = 3.125, rounded down = 3)
- Block X=-10 → chunk X=-1 (-10 / 16 = -0.625, rounded down = -1)
- Block X=16 → chunk X=1 (16 / 16 = 1.0, exactly on the border, so it is the first block of a new chunk)
You can see chunk borders in the game by pressing F3 + G (Java Edition), which draws lines along the borders between chunks.
What is a region and an .mca file?
A region is a group of 32x32 chunks (512x512 blocks). Minecraft saves world data in region
files, and each file is named r.X.Z.mca, where X and Z are the region coordinates.
The .mca (Minecraft Anvil) format has been in use since version 1.2.
Region coordinates are worked out like chunk coordinates: regionX = floor(chunkX / 32).
You will find region files in the region folder of each dimension (Overworld,
Nether and End) in your world save.
When do you need a region file?
- Deleting glitched chunks: If part of the world is corrupted, you can delete the region file and Minecraft will generate new chunks the next time you visit.
- Moving parts of a map: Copying an .mca file between worlds moves a whole section of terrain (512x512 blocks).
- Server optimization: Tools like MCAselector let you trim unused chunks from region files.
- Resetting chunks after an update: Deleting a region file far from your base lets you generate new terrain with new biomes and structures after a game update.
Slime chunks: mechanics and farms
Slime chunks are special chunks where slimes (green bouncing cubes) can spawn below Y=40. About 10% of all chunks are slime chunks. Which chunks are slime chunks depends on the world seed: the same seed always gives the same slime chunks.
In Java Edition, the slime chunk algorithm is based on Java's pseudorandom number generator (an LCG, or linear congruential generator). The formula combines the world seed with the chunk coordinates and checks whether the result modulo 10 equals zero.
How do you build a slime farm?
- Find a slime chunk with our calculator (the "Slime chunk" tab).
- Dig out a 16x16 area below Y=40, with 3 blocks of height for each spawning layer.
- Light the inside with torches. Light doesn't stop slimes from spawning, but it does stop zombies, skeletons and other mobs.
- Build platforms every 3 blocks of height - each platform is one spawning layer.
- Add a kill mechanism: magma blocks on the floor (slimes bounce onto them), a campfire, cacti, or a water system that leads down to a pit with magma blocks.
- Collect the slimeballs with hoppers connected to chests.
The more layers you dig out, the faster the farm. A farm across 4 adjacent slime chunks is the sweet spot: big enough to give you a surplus of slimeballs.
Where else do slimes spawn?
Outside slime chunks, slimes spawn naturally in swamp biomes on the surface at night (Y=50-70). The spawn chance depends on the moon phase: a full moon gives the highest spawn rate. But swamp spawns are much rarer than in slime chunks and harder to automate.
Converting Nether coordinates
Our calculator also has a built-in Nether converter. It works like the dedicated Nether portal calculator, but also shows chunk and region information.
The rule is simple: one block in the Nether equals 8 blocks in the Overworld. Divide the X and Z coordinates by 8 (Overworld → Nether) or multiply them by 8 (Nether → Overworld). The Y coordinate isn't converted.
The extra chunk and region information is handy when you want, for example, to find the region file that matches a given portal, or to check which chunk a portal sits in after the conversion.
The F3 debug screen: how to read your coordinates
In Java Edition, press F3 to open the debug screen. These are the most important lines for coordinates:
- XYZ: Your exact position (with decimals, which show where you are inside the block).
- Block: The coordinates of the block you are standing in (rounded down).
- Chunk: The chunk coordinates and your position inside the chunk (in the format X Y Z in X Y Z).
- Facing: The direction you are looking in (north/south/east/west).
In Bedrock Edition, turn on "Show Coordinates" in the world settings and the coordinates appear in the top left corner of the screen. Bedrock doesn't show chunk and region information, which is what our calculator is for.
Minecraft world data formats
Minecraft stores world data in the NBT (Named Binary Tag) format, grouped into region files:
- region - chunks of each dimension (r.X.Z.mca files)
- entities - entities (mobs, items on the ground), stored separately from chunks since 1.17
- poi - points of interest (beds, workstations, bells), since 1.14
- level.dat - the world's metadata
Tools such as NBTExplorer, MCAselector and Amulet Editor let you browse and edit these files. Our calculator helps you find the right region file when you need to modify a specific part of the world.
Practical uses of the calculator
Resetting terrain after an update
After a big Minecraft update (for example 1.18, 1.19 or 1.21), new biomes and structures only generate in new chunks. To get fresh terrain without losing your base, you can delete region files far from the base. Our calculator helps you work out which .mca file covers a given area of the map.
Building a slime farm
Find several neighboring slime chunks with the "Slime chunk" tab and its 7x7 map. The more slime chunks sit next to each other, the more efficient the farm. Our calculator shows a map of the surrounding area, so clusters of slime chunks are easy to spot.
Moving builds between worlds
Want to move a castle from one world to another? Work out which region files the build sits in, copy those files into the new world and you're done - the build appears in the same place (the same coordinates).
Frequently asked questions
How do I convert block coordinates to a chunk in Minecraft?
Divide the block coordinate by 16 and round down (floor). For example, block X=100 is in chunk X=6 (floor(100/16) = 6). Block X=-30 is in chunk X=-2 (floor(-30/16) = -2). Keep in mind that flooring a negative number rounds toward negative infinity.
What is a .mca region file in Minecraft?
A region file (.mca, short for Minecraft Anvil) stores 32x32 chunks (512x512 blocks). Files are named r.X.Z.mca, where X and Z are the region coordinates. You will find region files in the region folder of each dimension in your world save. They are useful for deleting glitched chunks, moving parts of a map or debugging.
How do I check whether a chunk is a slime chunk?
In Java Edition, slime chunks depend on the world seed and the chunk coordinates. The algorithm is based on Java's Random formula, so you can't judge it by eye in the game. Use our calculator: enter the seed (the /seed command) and the chunk coordinates, and the tool works out whether slimes can spawn there.
How do I work out the region from block coordinates?
First work out the chunk: floor(block / 16). Then the region: floor(chunk / 32). For example: block X=1000 → chunk X=62 → region X=1. The region file is r.1.Z.mca. Our calculator does this automatically and gives you the .mca file name.
How many blocks are in a chunk?
A chunk is 16 blocks wide (X) and 16 blocks deep (Z). Its height runs from Y=-64 to Y=320 (since version 1.18), which is 384 layers. In total, one chunk is 16 x 16 x 384 = 98,304 blocks. The chunk is the basic unit in which Minecraft loads the world.
At what depth do slimes spawn in slime chunks?
In slime chunks, slimes spawn below Y=40, regardless of the light level. Outside slime chunks, slimes spawn only in swamp biomes, on the surface at night between Y=50 and Y=70, when the moon phase is right.