What range of numbers can be converted to Roman numerals?

This tool converts standard Roman numerals in the classical range 1–3999 (I to MMMCMXCIX).

Can I convert Roman numerals back to Arabic numbers?

Yes. Enter a valid Roman numeral such as MCMXCIV and it will return 1994. The tool also flags invalid patterns.

Does it support dates?

Yes. You can enter a calendar date and convert day, month, and year into Roman numerals, often used for inscriptions.

Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals to numbers. Supports 1–3999, validation, and even date-to-Roman formatting. Includes rules, table of symbols, and FAQ.

Full original guide (expanded)

Roman Numeral Converter

Convert between Arabic numbers and Roman numerals, validate your Roman strings, and even convert dates like 2025-11-07 → VII • XI • MMXXV.

1. Number ➜ Roman

Enter a number (1–3999)

Roman numeral

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2. Roman ➜ Number

Enter a Roman numeral (I–MMMCMXCIX)

Arabic number

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3. Date ➜ Roman

Useful for inscriptions or fancy headings. We convert day, month, year separately.

Select a date

Date in Roman numerals

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Roman numeral rules

Roman numerals are built from these symbols:

Symbol	Value	Notes
I	1
V	5
X	10
L	50
C	100
D	500
M	1000
IV, IX	4, 9	Subtractive notation
XL, XC	40, 90	Subtractive notation
CD, CM	400, 900	Subtractive notation

This tool enforces standard modern form (no overlines, no 5000+, no non-standard repetitions).

Audit: Complete

Formula (LaTeX) + variables + units

This section shows the formulas used by the calculator engine, plus variable definitions and units.

Formula (extracted LaTeX)

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Variables and units

No variables provided in audit spec.

Sources (authoritative):

NIST — Weights and measures — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/weights-and-measures
NIST — SI units — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/owm/metric-si/si-units

Changelog

Version: 0.1.0-draft
Last code update: 2026-01-19

0.1.0-draft · 2026-01-19

Initial audit spec draft generated from HTML extraction (review required).
Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
Confirm sources are authoritative and relevant to the calculator methodology.

Verified by Ugo Candido on 2026-01-19
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Formulas

(Formulas preserved from original page content, if present.)

Version 0.1.0-draft

Citations

Add authoritative sources relevant to this calculator (standards bodies, manuals, official docs).

Changelog

0.1.0-draft — 2026-01-19: Initial draft (review required).