Chess Square Coordinate Parser

Parse a strict lowercase a1–h8 chess square into zero-based file and rank; no algebraic move parsing.

Description

Parse a strict lowercase a1–h8 chess square into zero-based file and rank; no algebraic move parsing.

A chess square label can be decomposed into zero-based file and rank coordinates.

When to use this tool

Parse a strict lowercase a1–h8 chess square into zero-based file and rank; no algebraic move parsing.

Prepare the supplied square fields for this operation.
Compare the complete example with the representation used by your own input before carrying the result into another step.

How to use the tool and how it works

Enter square. Use the exact text syntax, units and index conventions explained below.
Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
Read result.file, result.rank. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.

Require exactly lowercase a through h followed by 1 through 8. Return file as the letter offset from a and rank as the digit minus one.^[1]

Input field	Meaning and representation	Accepted input
square	square.	Text; at most 8,192 UTF-16 code units, subject to the grammar above

Output field	Interpretation
result	Object containing the named outputs below.
result.file	The file value under the stated formula or text convention.
result.rank	The rank value under the stated formula or text convention.

json

{
  "input": {
    "square": "c4"
  },
  "output": {
    "result": {
      "file": 2,
      "rank": 3
    }
  }
}

Limitations and assumptions

Uppercase, surrounding whitespace and move notation are rejected. The result is a location rather than a move-validation result.
Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
Lists are limited to 128 entries. JSON text must meet bounded size and depth checks, and numeric outputs beyond the safe finite magnitude are rejected. Exact large integers use decimal strings.
Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.

Alternative or Complementary methods

Use a game-state-aware rules engine when occupancy, legal moves or scoring rules matter. These operations calculate coordinates, local geometry or supplied ledger totals without inferring a complete position.

References

Tool behavior and example: Chess Square Coordinate Parser — tool.io

Similar or alternative tools

Chess Square Coordinate Formatter
Format validated zero-based 8×8 chess file/rank coordinates as a lowercase square token.
Board Coordinate Mirror Tool
Mirror zero-based rectangular board cell coordinates across explicitly selected board centerlines; no piece-state transformation.