Convert Arabic integers (1–3999) to canonical subtractive Roman numerals and parse Roman text back — with strict validation, debounced two‑way sync, and one‑click copy. Everything runs in your tab: the same local-first approach as APK Analyzer and APK String Extractor — no uploads.
Allowed range: 1–3999. Zero and negatives are not valid in this classical subset.
Letters I V X L C D M only; uses subtractive pairs (IV, IX, …). Whitespace is ignored.
You can think of it as a bidirectional formatter: type 1987 and get MCMLXXXVII, or paste MCMLXXXVII and recover
1987. Parsing uses a strict pattern so only modern subtractive spellings count as valid — parallel to how
APK Analyzer prefers clear structure over guessing ambiguous archive bytes. No server sees your input.
Today’s usual rules allow six “subtractive” pairs: IV (4), IX (9), XL (40), XC (90), CD (400), and
CM (900). Older additive forms (like four tally marks for 4) are rejected here so output always round-trips cleanly.
With the letters M D C L X V I alone, canonical modern notation conventionally stops at MMM for thousands plus the normal hundreds/tens/ones pattern
(MMMCMXCIX = 3999). Beyond that, typography uses vincula, overbars, or other extensions that are not unique across textbooks — so this tool keeps a single, unambiguous rule set.
2024 = MMXXIV, or Use current year for a quick demo.No. Parsing and formatting run only in your browser with JavaScript — the same local-first model as APK Analyzer and APK String Extractor.
Classic Roman notation with standard letters traditionally tops out at 3999 (MMMCMXCIX). Larger values use conventions like vincula or special notations that vary by source; this tool stays strict to avoid ambiguous output.
Only well-formed modern subtractive notation is accepted (for example IV for 4, IX for 9, XL, XC, CD, CM). Non-canonical spellings such as IIII for 4
are rejected so round-trips stay predictable.
No. The Romans did not use a widespread zero symbol in this system; enter positive integers from 1 upward.
Yes — input is normalized to uppercase before validation (xl → XL).
Clock faces often use IIII for stylistic symmetry; that is not the standard subtractive form this validator accepts.
No. It follows the common “modern” rules taught in schools and used in most software — not every historical manuscript convention.
Whitespace is removed before validation. Other stray characters will make the Roman side invalid until you clean them.
Yes: your inputs never leave the tab for conversion. Only normal static assets load from DroidXP like any page.
It is a study helper — always double-check against your instructor’s notation rules if they allow non-standard forms.