Map tiles covering a box

Model: The tiles from the one holding the northwest corner to the one holding the southeast corner, on the spherical Web Mercator grid; a box edge on a tile edge does not take the next tile

Show your work

1. Columns and rows

   the tiles holding the northwest and southeast corners

   x 4550 to 4552, y 6175 to 6177 = 3 × 3

2. Tiles

   $$\mathrm{columns}\times \mathrm{rows}$$

   3 × 3 = 9

The same steps an agent gets from the MCP server with explain: true.

Accuracy: Exact; latitudes beyond ±85.0511° are clamped to the Web Mercator limit

When to use this: Use this to list the tiles an area needs: pre-caching a region for offline use, planning a download, working out how much a basemap job will cost, or invalidating everything that covers a changed area. Give the box and the zoom and it returns every tile that touches it.

Limitations: The grid ends at plus or minus 85.0511 degrees, where the Web Mercator square runs out; a box beyond that is clamped, with a warning, because there are no tiles there. A box edge lying exactly on a tile edge does not take the next tile, so a one-tile box returns one tile. West greater than east means the box crosses the antimeridian and the columns wrap. The count grows fourfold per zoom, so a wide box at a deep zoom is refused rather than answered with a list nobody wanted.

Worked example: Downtown Pittsburgh at zoom 14. Source: Slippy map tile arithmetic. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

Review: Not yet independently reviewed by a GIS professional.

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.0.0, core 0.1.0. See this tool in the verification report.

Checked against: 21 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

• Slippy map tilenames, OpenStreetMap Wiki, Current wiki page. Lon./lat. to tile numbers, tile numbers to lon./lat., resolution and scale.
• Bing Maps Tile System, Microsoft, Online documentation. Tile coordinates and quadkeys; ground resolution = cos(lat) × 2π × 6,378,137 / (256 × 2^level).