Convert Excel column letters to numbers and numbers to letters

Enter letters such as A, Z, AA, or XFD to receive the corresponding positive column number, or enter a number such as 1, 27, or 16384 to receive its letter reference. It handles lowercase letters and surrounding spaces, returns a clear result that is easy to use in code, and rejects malformed letters, zero, negative values, decimals, and numbers too large for safe integer arithmetic.

Convert a column letter into its number

Enter a letter reference exactly as it appears above a spreadsheet column, without a row number or cell punctuation. A becomes 1, Z becomes 26, AA becomes 27, and the pattern continues for longer references. Lowercase input is accepted and normalized to uppercase in the result, while spaces immediately before or after the reference are ignored. The conversion is based on a one-indexed alphabetic system rather than ordinary base 26: there is no zero digit, so Z is followed by AA instead of BA. This distinction matters when you are implementing imports, generating formulas, or translating user-facing spreadsheet coordinates into array offsets. The response includes both the normalized column letter and its positive column number, making the direction and the result explicit. Inputs containing digits mixed with letters, punctuation, spaces inside the reference, a dollar sign, or a row suffix are rejected. For example, use AA rather than AA12 or $AA, because this tool converts column references rather than complete cell addresses.

Convert a number into a column letter

Enter any positive whole number that can be represented safely by JavaScript, either as a numeric value through the API or as digits in the text field. The converter repeatedly maps the one-based remainder to A through Z, producing the same labels used by Excel and other spreadsheet programs. Thus 1 returns A, 26 returns Z, 27 returns AA, and 52 returns AZ. Zero and negative numbers are invalid because spreadsheet columns begin at one. Decimal values, exponential notation, signs, separators, and unsafe integers are also rejected rather than rounded or guessed. Although modern Excel worksheets have a product-specific final column, this converter intentionally implements the general letter-number notation and does not impose a particular application version's worksheet limit. That makes it useful for generic tabular systems and algorithms that use the same naming convention. If your destination has its own maximum column count, validate that business limit separately after conversion. The returned object contains the original numeric meaning alongside the generated uppercase letters.

Use reliable conversions in spreadsheet workflows

Column conversion is a small operation that often sits inside larger automation: building ranges, mapping CSV headers, creating spreadsheet formulas, interpreting configuration files, or displaying friendly coordinates in a user interface. Keeping it as a deterministic capability prevents different services from implementing subtly different rules around Z, AA, and later boundaries. The algorithm uses no network requests, randomness, current time, external workbook, or stored state, so identical input always produces identical output. Validation is deliberately strict. If a value looks like neither a positive integer nor letters A through Z, the request fails with an invalid-input error instead of silently changing the value. This behavior is especially helpful in pipelines, where an early error is easier to diagnose than a formula aimed at the wrong column. Interactive use is available directly in the browser, while an API request costs $0.002. For bulk work, call the capability once for each reference and retain the returned number-letter pair wherever downstream steps need an auditable mapping.