Overview
Introduction
This tool parses English ordinal strings like "1st", "2nd", "3rd", and "21st" back into their plain integer values, while double-checking that each one uses the grammatically correct suffix.
It's the reverse of the Integer to Ordinal Converter, and unlike a simple suffix-stripping approach, it actively rejects malformed ordinals such as "21th" or "2st".
What Is Ordinal to Integer Converter?
A converter that takes a list of ordinal strings, one per line, and outputs the plain integer each one represents, after validating the suffix.
It applies the same English ordinal suffix rules (including the 11th/12th/13th exceptions) in reverse, to check correctness rather than assume it.
How Ordinal to Integer Converter Works
Each line is matched against a pattern of one or more digits followed by "st", "nd", "rd", or "th" (case-insensitive).
The tool computes what the correct suffix should be for that specific number, using the same modulo-100 and last-digit logic as the forward converter.
If the provided suffix doesn't match the computed correct one, the line is rejected with an error explaining the mismatch; otherwise, the plain number is returned.
When To Use Ordinal to Integer Converter
Use it to parse ordinal text (like "3rd place" or "the 21st") back into a number you can sort, compare, or calculate with.
It's also useful for validating that ordinal strings elsewhere in your data use correct English grammar.
Often used alongside Integer to Ordinal Converter and Fraction to Integer Converter.
Features
Advantages
- Catches grammatically incorrect ordinals instead of silently accepting any suffix.
- Reuses the same correct suffix rule (including the teens exception) as the forward converter, so the two tools stay consistent.
Limitations
- Only understands English ordinal suffixes; ordinals from other languages aren't supported.
- Requires the ordinal to be written with digits (like "21st"), not spelled out (like "twenty-first").
Examples
Best Practices & Notes
Best Practices
- If you're generating ordinal strings programmatically to feed into this tool, use the companion Integer to Ordinal Converter so the suffixes are always correct.
Developer Notes
The validation reuses the exact same suffix-selection logic as the Integer to Ordinal Converter (checking `n % 100` for the 11-13 exception, then `n % 10` otherwise) and compares it against the parsed suffix, so both tools agree on what counts as "correct".
Ordinal to Integer Converter Use Cases
- Parsing ordinal text like "3rd" or "21st" back into a sortable or computable number
- Validating that ordinal strings in a dataset use grammatically correct suffixes
- Checking round-trip correctness against the Integer to Ordinal Converter
Common Mistakes
- Assuming any suffix will be accepted for a given number; only the grammatically correct one passes.
- Entering a spelled-out ordinal like "twenty-first" instead of the digit form "21st".
Tips
- If a line is rejected, check whether the number falls in the 11-13 (or 111-113, etc.) exception range before assuming the suffix is simply wrong.