Nether Portal Calculator
Overworld to Nether and back, plus the collision check nobody else does.
The conversion itself is a division by eight: the Nether is eight times smaller than the Overworld on X and Z, and Y is the same in both. That part is easy, and every calculator gets it right.
What goes wrong is linking. When you walk through a portal, the game looks for an existing portal within 128 blocks of the arrival point in the destination dimension, and uses that one if it finds it. Two Overworld portals less than 1,024 blocks apart land inside the same 128-block box in the Nether, so the second one you build quietly hijacks the first one's destination. That is why your base portal starts spitting you out at your friend's mine.
Build the Nether side by hand at the exact coordinates below, and keep portals you want kept separate more than 1,024 Overworld blocks apart.
More about Minecraft
Tools
Common questions
Does this work for Bedrock as well as Java?
Yes. The 8:1 ratio and the 128-block search box are the same in both editions, and have been since Nether portals existed.
Why did my portal link to the wrong place?
Because a portal already existed within 128 blocks of where you arrived. The game reuses it rather than building a new one. Break the unwanted portal, or move yours more than 1,024 Overworld blocks away.
Do I need to build the Nether side at all?
No, but you should. If you let the game generate it, it places the portal wherever it finds room, which is often inside a wall or above lava, and the return trip lands somewhere you did not choose.
Does Y matter?
It is carried across unchanged, but the Nether roof is at Y=128, so anything higher than that in the Overworld will be placed lower. Build it manually at a height you pick.
Figures checked on Aug 22, 2026 against minecraft.wiki
Game names are used to identify what these tools calculate for. SV.GAMES is not affiliated with, endorsed by or sponsored by any publisher.