Nether Portal Size Calculator

1. Choose Outer frame or Inner opening. The same portal is shown either way, but outer dimensions include the obsidian edge while the opening is the clear space inside.
2. Enter a whole width and height inside the displayed range. The blueprint updates block by block.
3. Choose whether to skip or include the four corner blocks. This changes the obsidian total by 4, not the opening size.
4. Read the required obsidian, opening area, and stack breakdown, then copy the material list or text blueprint if you want it beside the build.

The minimum facts are 4×5 outer with 10 obsidian without corners; the maximum is 23×23 outer with 84 obsidian without corners. Those numbers are calculated from the same frame model used by the tool.

A standard vertical Nether portal uses an outer frame from 4 to 23 blocks wide and 5 to 23 blocks tall. The opening is always two blocks smaller on each axis, so the smallest opening is 2×3 and the largest is 21×21.

A 5-wide × 4-tall frame is not valid because 4 is below the minimum outer height. The opposite mistake is treating 23×23 as an opening: 23×23 is the outside limit, and a 23×23 clear opening would require a larger frame than vanilla allows.

Modern Java and Bedrock use the same standard frame range. This page does not show an edition toggle because frame sizing does not change between them. Linking behavior and some other portal mechanics can still differ.

For one standalone rectangular frame, count the perimeter. With W as outer width and H as outer height:

obsidian with corners = 2W + 2H − 4
obsidian without corners = 2W + 2H − 8

The minimum 4×5 frame therefore needs 10 obsidian without corners or 14 with them. The maximum 23×23 frame needs 84 without corners or 88 with them.

At the maximum, 84 blocks is 1 stack + 20 blocks. The complete-corner version, 88 blocks, is 1 stack + 24 blocks. A square 10×10 frame uses 32 without corners and has a 8×8 opening.

These are exact counts for one isolated portal frame. If frames share obsidian edges in a larger build, the amount you place can be lower; this calculator does not claim to optimize shared blocks. Portal interior blocks are not inventory obsidian, so they are reported as opening area instead.

These useful frame sizes are calculated at page build time from the same formulas as the interactive tool. They are not copied totals from a separate table.

1. Place the bottom row of ordinary obsidian to the chosen outer width.
2. Build both vertical sides up to the chosen outer height, including or skipping the corners.
3. Close the top row so the required perimeter is complete and the interior is clear.
4. Light fire inside the finished opening with flint and steel or a fire charge.

Nether portals are upright vertical rectangles, not flat horizontal frames. Placing obsidian alone does not activate the portal; the fire must be inside a complete frame. See the Minecraft Wiki Nether portal reference for the structure rules.

Crying obsidian cannot replace ordinary obsidian on the required functional edges. It appears in ruined portal structures and can be used as unrelated decoration, including optional corner positions, but the working edge needs regular obsidian.

• Confusing the outer frame with the opening, then building a frame two blocks too small.
• Treating 23×23 as the opening instead of the maximum outside measurement.
• Trying a 5-wide × 4-tall frame, which fails the minimum height.
• Leaving a gap in a required edge because “the corner is optional” was applied to the wrong block.
• Using crying obsidian where the frame needs ordinary obsidian.
• Digging a flat horizontal frame or building it in the End.
• Filling the opening with obsidian and expecting it to activate.
• Assuming a larger frame forces a particular linked destination.

Frame size does not create a separate set of coordinate rules. The exact portal block you enter can still affect a trip, and a wide frame can present more than one entry position. Do not describe a large frame as purely cosmetic with guaranteed identical linking. See the Minecraft Wiki Nether portal reference for the documented mechanics.

This calculator does not simulate linking. If you already know your portals, use the Nether portal link checker to compare entered portals, edition-specific search areas, Y distance, and the return trip. Its results are representative-point estimates, not guarantees.

The calculator normalizes every input to one outer frame state. Outer width W and height H must be integers from 4–23 and 5–23. Opening mode accepts 2–21 and 3–21, then adds 2 to each axis. The opening area is (W−2)(H−2), and the obsidian formula is 2W + 2H − 4 with corners or 2W + 2H − 8 without them.

The blueprint generates exactly W×H cells. Perimeter cells are obsidian, interior cells are opening, and the four corners are omitted or obsidian depending on your choice. Tests compare every one of the 380 valid width/height combinations against the cell grid, so the diagram and material count cannot silently diverge.

The optional budget planner enumerates all 380 outer frames, keeps those whose required obsidian fits your budget, and ranks by largest opening area, fewer required blocks, a squarer opening, then smaller width and height. It plans one standalone new frame only.

All calculations run in the browser. No portal coordinates are needed, nothing is uploaded, and this page does not store a build. The math is exact for an isolated vanilla-style rectangular frame; terrain, mods, shared multi-portal edges, and the actual linked destination are outside its scope. Read the site calculation methodology for the shared validation and testing approach.

Sources

• Minecraft Wiki: Nether Portal— Frame dimensions, obsidian counts, and the 8:1 dimensional ratio.
• Minecraft Wiki: Nether portals tutorial— Portal linking behavior, candidate search areas, and edition differences.
• Minecraft Wiki: Nether survival tutorial— Portal construction examples, minimum frame, and ruined-portal repair.
• Minecraft Wiki: Crying obsidian— Crying obsidian cannot replace the functional frame edges.
• Minecraft Wiki: Ruined portal— Ruined structures may contain crying obsidian and need repair before use.
• Minecraft Wiki: Point of Interest— Portal blocks as points of interest used by the game search.
• Minecraft Wiki: Nether hub tutorial— Converting endpoints and building routes between Nether portals.
• Minecraft Wiki: Player movement— Nominal walking and sprinting movement speeds.
• Minecraft Wiki: Blue Ice— Blue-ice boat transport reference and top-speed context.
• Minecraft Wiki: Transportation methods— Packed-ice and blue-ice boat transport comparisons.

Minecraft Wiki is a community-maintained reference, not official Mojang documentation. No in-game Java or Bedrock test was performed for this page; the geometry is verified by automated tests against the documented rules above.

Calculate where to build your Nether portal with the homepage coordinate converter, then check which existing portal may connect if you already have a portal network.

Connecting two builds? Plan travel between two portal locations with a two-point Nether route, axis directions, and material estimates.