Nether Portal Calculator

Understanding portal mechanics

Nether portals connect the Overworld and the Nether at a fixed 8:1 ratio — one block travelled in the Nether covers eight in the Overworld, which is what makes it a fast-travel network. Height is the exception: Y is carried across unchanged, so the two portals should sit at the same height wherever the Nether has room for it.

Portal construction

• ▸ The smallest portal is 4×5 blocks including the frame, which costs 10 obsidian if you leave the corners out
• ▸ Portals can be built up to 23×23 blocks
• ▸ Light the inside with flint and steel or a fire charge
• ▸ Build both ends at the calculated coordinates so they pair up instead of spawning new portals

Troubleshooting links

• ▸ A portal in the Overworld looks for an existing Nether portal within 128 blocks of the calculated spot, and builds a new one if it finds nothing
• ▸ Coming back the other way, the search radius is 1024 blocks
• ▸ Two portals closer than 128 blocks in the Nether will fight over the same link — space them out
• ▸ The Nether only spans Y 0–127, and bedrock fills the top layers, so a portal near the roof will not link

Before you go through

• ▸ Spare obsidian and a flint and steel, in case the far side spawns somewhere unusable
• ▸ Blocks to bridge with, and a way to block off the portal room
• ▸ Fire resistance potions and a gold item or two to keep piglins friendly
• ▸ Never carry a bed — it explodes in the Nether