X and Z are divided (or multiplied) by 8 and shown rounded to whole blocks; Y never changes. Stand at your portal, press F3 (Java) to read your coordinates, and build the far end exactly at the result.
| Fact | Value |
|---|---|
| Scale (X and Z) | 1 Nether block = 8 Overworld blocks |
| Y coordinate | Unchanged between dimensions |
| Portal search range on crossing | ~128 blocks (Overworld) / ~16 blocks (Nether) |
| Nether ceiling (Java) | Bedrock roof at Y=128 |
| 1,000-block Overworld trip | 125 blocks through the Nether |
Random portal pairing is the top cause of "my portal sent me somewhere else". The fix is deterministic: pick the Overworld spot, convert it here, and place the Nether frame at exactly the converted X/Y/Z before you ever step through. Do the same for every base and hub on the server and your Nether becomes a clean 1:8 subway map instead of a maze of stray portals.
The Nether is scaled 1:8. Divide your Overworld X and Z by 8 (Y stays the same) to get the matching Nether position; multiply by 8 to go the other way. Travelling one block in the Nether covers eight blocks in the Overworld, which is why Nether highways are so fast.
When you cross, the game looks for an existing portal near the converted coordinates — within roughly 128 blocks on the Overworld side and 16 blocks in the Nether. If your intended portal sits outside that range (usually an off-by-8 X/Z or a very different Y), the game generates a fresh one instead.
No — Y is copied as-is, only X and Z are scaled. Keep in mind the Nether's usable space ends at the bedrock roof (Y=128 in Java Edition), so pick a height that exists comfortably in both dimensions.
Build both ends by hand. Convert your Overworld coordinates with the calculator, travel to exactly that X/Y/Z in the Nether (tunnel there if needed), build the frame and light it. Hand-placed pairs at matching converted coordinates always find each other.