Nether Portal Calculator

The Nether is eight times smaller than the Overworld along X and Z. One block in the Nether covers eight in the Overworld, so a short walk in the Nether crosses a long way above. The nether portal calculator divides each Overworld horizontal coordinate by 8 and rounds down to get the Nether ones, and multiplies each Nether one by 8 to go back. Y is not scaled, so a portal at Y 64 stays at Y 64.

Rounding down means negative numbers go one block further from zero than you might expect: Overworld X −1 is Nether X −1, and Overworld X −9 is Nether X −2. It also means eight Overworld blocks share every Nether block. Nether X 125 covers Overworld X 1000 to 1007, and the calculator prints that range under the boxes.

Bedrock and Java use the same 1:8 ratio, so this Overworld to Nether calculator works in both. Coordinates past the world border are put on the border, and Nether coordinates stop at ±3,749,998, because eight times more would leave the world.

The nether portal calculator sizes the frame too. A Nether portal is a rectangle of obsidian with an empty opening inside. Java Edition has allowed frames from 4 × 5 to 23 × 23 blocks since snapshot 13w37a, and Bedrock Edition lists the same limits. Those numbers count the frame from the outside, so the opening is from 2 × 3 to 21 × 21. The four corner blocks of the frame are not needed for the portal to light, although portals the game generates always have them.

The obsidian count is 2 × (width + height) + 4 with the corners, or 2 × (width + height) without, where width and height are the opening. The smallest frame takes 14 obsidian, or 10 without corners. A 10 × 10 opening takes 44, and the biggest possible frame takes 88. Portal blocks fill the opening, so a 2 × 3 opening holds 6.

Choose the size with the width and height boxes and switch the corners on or off. The drawing shows which blocks to place, and the .litematic button gives you the frame as a wall for Litematica.

When you step into a portal, the game converts your position as above and looks for a portal near it in the other dimension. In Java Edition the search reaches 128 blocks around the converted position in the Overworld and 16 blocks in the Nether; the Nether range was cut from 128 to 16 in Java 1.16.2 (snapshot 20w28a) to match the 1:8 scale. In Bedrock Edition the search reaches 128 blocks in both dimensions. The search covers the full height of the world.

If several portals are in range, the game picks the closest one by straight-line distance, and the height counts, so a portal that looks further away on the map can win. If there is none, the game builds a new portal within 16 blocks of the converted position. This is why a Nether portal built at the converted coordinates is the safest way to make a link you can predict, and why a nether coordinate calculator like this one is the first tool for a portal network.

A portal built in the Nether that is wider than 18 blocks connects each end to a different Overworld portal.

• Nether highways. Build a portal near your base, note its Nether coordinates and build a second portal near a far-off Overworld target. A 1,000-block trip is a walk of 125 blocks in the Nether.
• Base hubs. Give every base a portal at coordinates that are multiples of 8 so the Overworld and Nether positions line up exactly.
• Farms and spawners. Put a portal next to a farm and write both coordinate sets down, so you can always find your way back.
• Big gates. A 21 × 21 opening is a spectacular gate, at the price of 88 obsidian, which is one stack and 24 blocks.

Use the coordinates from the F3 screen and type them as they are; decimals are fine, and the calculator rounds down like the game does. When you lay out a portal network, write both coordinate sets down and check with this nether portal calculator that no two Nether portals are close enough to be picked instead of each other. Adjacent portals can share obsidian, which saves blocks.