Minecraft Nether Portal Calculator
Plan a real Minecraft Nether portal before mining obsidian. Change the opening size, decide whether to include corners, and inspect every block of the vertical frame.
The purple region is the portal opening. Corners are optional. Ignite the finished vertical frame in a permitted dimension; this calculates the frame only, not exact portal linking or a safe destination.
How much obsidian do you need?
The smallest portal opening is 2 blocks wide and 3 tall. Without the four optional corners the frame requires 10 obsidian; a complete rectangular frame uses 14. The calculator is based on the frame border rather than estimating filled area.
What the dimensions mean
Choose the size of the purple interior. The outer frame is two blocks wider and two taller. A maximum supported frame is 23 × 23 blocks, so the largest interior here is 21 × 21.
Why linked portals may differ
Overworld and Nether coordinates are related by an 8:1 horizontal scale, but nearby portals, location constraints and game logic can affect the actual destination. Use the existing Nether coordinate converter for planning X/Z, not as a guarantee of precise link behavior.