Nether portals that link where you want them to — the 1:8 rule in practice
Portals do not pair by coordinates alone. Here is the search box the game actually checks, why your portal keeps connecting to the wrong one, and how to force a clean pair.
The maths everyone knows is Overworld ÷ 8 = Nether. The part that trips people up is what happens after that division: the game does not build a portal at those exact coordinates. It searches.
What the game actually does
When you step into a portal, Minecraft converts your coordinates, then looks for an existing portal inside a search box around the target:
- 33×33 blocks horizontally when you arrive in the Nether (16 each way), and 257×257 when you arrive in the Overworld (128 each way), centred on the converted position
- the full height of the destination dimension
If it finds one, you come out there — even if that portal is 100 blocks from where you wanted (in the Overworld; in the Nether it is at most 16 blocks off on each axis). Only if the box is empty does it build a new portal.
That single rule explains almost every "my portals are linked wrong" report.
Why two Overworld portals share one Nether portal
Two Overworld portals 100 blocks apart convert to Nether positions about 12 blocks apart. Twelve is inside the 16-block Nether search, so both find the same Nether portal and both come out there. From the Overworld they feel unrelated; in the Nether they are neighbours.
Rule of thumb: Overworld portals need to be more than 128 blocks apart on some axis to get separate Nether-side destinations (128 ÷ 8 = 16, the edge of the Nether search).
Forcing a clean pair
- Build the Overworld portal, note X and Z.
- Divide both by 8 and round down (toward negative infinity — −1 stays −1, not 0). That is your Nether target.
- Go to the Nether and build the portal there manually, at those coordinates, before ever using the Overworld one.
- Light it. Now walk through the Overworld portal — it finds yours and links.
Building the second side by hand is the whole trick. Let the game generate it and you inherit whatever it finds first.
Y matters less than you think
Vertical position is not part of the 1:8 conversion — Y is carried across unchanged and then clamped to the destination's buildable range. Two portals stacked at Y=30 and Y=100 in the Nether are both inside the same horizontal box, so they compete.
Roof travel
Nether ceiling highways work because 1 block up there equals 8 in the Overworld. A 1,000 block walk on the roof moves you 8,000 blocks at home. The portal search box is what decides where you land, so space your roof portals at least 17 blocks apart (17 × 8 = 136, outside the Overworld's 128-block search) or they will collapse into each other.
Put your real coordinates into the Nether Portal Calculator — it converts both directions and draws the real search range — 128 blocks in the Overworld, 16 in the Nether — on a to-scale map, so you can see whether two portals will fight before you build them.