Building

Nether Portal Frame Calculator

Count obsidian and portal interior blocks for custom frame sizes.

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Your Minecraft mission

Outer widthOuter height

Obsidian (no corners): 10
Obsidian (all corners): 14
Valid vanilla size: Yes

Game rule: Vanilla portal interiors are 2×3 through 21×21, so outer frames are 4×5 through 23×23.

Step-by-step guide

How to use the Nether Portal Frame Calculator

Enter the complete outside frame width and height.
Choose the obsidian count with all corners or with four optional corners removed.
Confirm the outside dimensions fall inside the vanilla valid range.

Calculation

Formula and game rule

With corners: 2W+2H−4. Without corners: 2(W−2)+2(H−2). Interior area: (W−2)(H−2).

Worked example

Example result

The minimum 4×5 outside frame needs 14 obsidian with corners or 10 without corners and has a 2×3 interior.

What to check before using the result

Width and height refer to the outside edge of the obsidian frame, not the purple interior.
Decorative obsidian outside the required rectangular frame is not included.

Java and Bedrock Edition

The calculator accepts vanilla outer frames from 4×5 through 23×23 used by current Java and Bedrock portals.

This page is designed for players looking for a Minecraft portal size calculator, obsidian calculator, Nether portal dimensions. The calculator runs locally in your browser and updates without sending your world coordinates or command inputs to the server.

Common questions