The rule
Overworld → Nether: X ÷ 8, Z ÷ 8, round down. Nether → Overworld: X × 8, Z × 8. Y stays the same in both directions.
Worked examples
| Start | Calculation | Result |
|---|---|---|
| Overworld 800, 64, −1200 | 800 ÷ 8 = 100, −1200 ÷ 8 = −150 | Nether 100, 64, −150 |
| Overworld −45, 70, 13 | −45 ÷ 8 = −5.625, 13 ÷ 8 = 1.625, round both down | Nether −6, 70, 1 |
| Nether 37, 90, −12 | 37 × 8 = 296, −12 × 8 = −96 | Overworld 296, 90, −96 |
Rounding negative numbers
The game always rounds down, towards negative infinity. For positive numbers that is the same as dropping the decimals, but not for negative ones: −5.625 rounds down to −6, not −5. Getting this wrong puts a Nether portal one block off on each negative axis, which is enough to link to the wrong portal.
Going from the Nether to the Overworld never needs rounding, because multiplying a whole number by 8 gives a whole number. It does mean one Nether block matches an 8 × 8 area in the Overworld.
Building two portals that link
- Stand in your Overworld portal and read the Block line on the debug screen (F3 in Java Edition).
- Convert X and Z with the calculator. Keep the same Y if the Nether has space there.
- In the Nether, build the portal at those coordinates, or as close as the terrain allows.
- Walk through both ways and check you arrive in the portal you built.
How the game picks a portal (Java Edition)
When you use a portal, the game converts your position and looks for an existing portal near that point: within 16 blocks horizontally in the Nether, or 128 blocks in the Overworld, at any height. It uses the closest one, measured in a straight line including height. If there is none, it builds a new portal nearby.
That’s why an old portal can take over your new one. Why your Nether portal links to the wrong place covers the fixes.
Bedrock Edition
Bedrock uses the same 1:8 conversion. Its portal search is different: it looks up to 128 blocks away in both dimensions, so portals close together in the Nether are more likely to share a destination.
Limits
- The world border sits at X and Z ±29,999,984, so Nether coordinates beyond ±3,749,998 have no matching Overworld position inside the border.
- Height isn’t scaled, but the Nether is only 256 blocks tall with a bedrock roof at around Y 127. When the same Y isn’t possible, build the Nether portal as close to it as you can.