Pick a frame size from the smallest 4 × 5 to the largest 23 × 23 and see exactly how much obsidian you need, with or without the corners. A block preview shows the frame.
- Obsidian
- 10
- Portal opening
- 2 × 3
- Stacks
- 1
How much obsidian does a nether portal need?
The smallest portal is a 4 × 5 frame. It needs 10 obsidian without corners or 14 with corners. The biggest is 23 × 23: 84 obsidian without corners, 88 with. The formula is 2 × width + 2 × height − 8 (add 4 for corners).
Do the corners matter?
No. Corner blocks are optional on every edition; they only change the look. Skip them to save 4 obsidian.
How to use the nether portal size calculator
- Drag the width and height sliders (outer frame size, in blocks).
- Tick “Include the 4 corners” if you want a full frame.
- Read the obsidian total, or type how much you have to see the biggest portal you can build.
Nether Portal Size Calculator FAQ
What is the smallest nether portal?
An outer frame of 4 wide by 5 tall, which leaves a 2 × 3 opening. It needs 10 obsidian.
What is the biggest nether portal?
An outer frame of 23 × 23 blocks, with a 21 × 21 opening. It needs 84 obsidian, or 88 with corners.
How do I light a nether portal?
Use flint and steel or a fire charge on the inside of the frame. Fire from lava or a burning block also works.