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Roman Numeral Converter

Enter a number or Roman numeral for two-way conversion, review canonical validation and decomposition, or use the built-in date section to format a calendar date as Roman numeral month/day/year components.

Two-way conversion

Number (1–3,999,999)

Roman numeral

Quick conversion supports the same 1–3,999,999 vinculum range in both directions when Roman Numeral Studio is loaded; use the Studio below for strict canonical evidence and a plain-text underscore fallback.

Result

MMXXVI

2,026 in Roman numerals

Date in Roman numerals

Date

Order

Delimiter

Roman date

This converts the numeric date components; historical Roman inscriptions used many conventions rather than one universal modern date format.

Core symbols

X10

L50

C100

D500

M1,000

Canonical conversion + vinculum audit + date and reference workflows

Roman Numeral Studio

Convert either direction through 3,999,999, read Unicode combining-overline or underscore vinculum fallback, distinguish a readable numeral from the modern canonical spelling, inspect every add/subtract step, then carry the same verified value into dates, Roman arithmetic, batch audits and reference ranges.

Auto-detect number / Roman1–3,999,999 both waysUnicode + _I_V fallbackStrict vs readable auditDate engraving cardRoman math500-row batch + range CSV20 local recent conversions

1. Convert, decode & validate

Enter an Arabic whole number, standard Roman text, combining-overline vinculum, Unicode Roman compatibility characters, or an underscore fallback such as _I_V.

Modern canonical audit

Number or Roman numeral

Ready for local canonical verification.

Arabic value—

Canonical Roman—

Plain-text vinculum fallback—

Strict status—

Detected direction—

—

Token	Value	Operation	Running total

A form can be numerically readable without being canonical. Example: IIII is read as 4 here but canonicalized to IV; IM is readable as 999 but canonicalized to CMXCIX. Clock faces and historical inscriptions may intentionally use other conventions.

2. Date engraver

Convert each Gregorian date component without fake leading zeroes, choose order and separator, then copy or export a clean local SVG/PNG card.

DateOrderSeparatorRoman date

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3. Roman arithmetic

Use Arabic numbers or Roman inputs on either side. Exact positive whole-number results through 3,999,999 get a canonical Roman result; fractions, zero and negatives remain numeric instead of inventing a Roman form.

First operandOperationSecond operand

Numeric result—

Roman result—

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4. Local recent conversions & project

The latest 20 analyzed values are stored only in this browser. Project JSON can carry the current workspace deliberately; the portable URL carries settings only.

Project imports are capped at 1 MB. The share hash excludes conversion input, date, math operands, batch text, project content and local history.

5. Batch canonical audit

Paste numbers or Roman numerals separated by lines or commas. Each row is auto-detected and classified as canonical, readable/noncanonical, or invalid. The first 500 entries are processed per run.

Batch input

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Input	Value	Canonical	Strict?	Status	Evidence

6. Custom Roman reference range

Generate a focused number→Roman chart in either direction. Long requests are intentionally capped at 500 rows so a reference task does not freeze the page.

StartEnd

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Number	Unicode Roman	Plain-text fallback

Notation boundary. The Studio uses a documented modern canonical spelling policy: I, V, X, L, C, D, M with IV/IX/XL/XC/CD/CM, and for 4,000–3,999,999 a combining overline (vinculum) that multiplies a symbol by 1,000. Historical Roman inscriptions used additional additive, apostrophus and regional conventions, so this is not an epigraphic authentication tool. Roman numerals have no canonical modern zero or negative sign. Date boundary. Date mode converts components of a valid proleptic Gregorian date; it does not claim ancient Romans wrote calendar dates in this modern numeric order.

How to use the Roman Numeral Converter

For a fast answer, use the converter at the top. For a documented result, use Roman Numeral Studio: type either a whole number or Roman numeral and the page detects the direction, resolves the Arabic value, shows the canonical Roman spelling, and audits each token. Extended values through 3,999,999 can be written with combining overlines such as I̅V̅ or the copy-safe underscore fallback _I_V for 4,000.

Canonical Roman numeral rules used here

The modern standard symbols are I=1, V=5, X=10, L=50, C=100, D=500 and M=1,000. This page uses the usual subtractive pairs IV, IX, XL, XC, CD and CM. It can still read many noncanonical spellings and then explicitly shows the canonical replacement instead of silently pretending the input is standard.

Why IIII can still appear on clocks

Many clock faces use IIII for four even though modern conversion exercises normally use IV. That is a display tradition, not evidence that every additive spelling should pass strict canonical validation. The Studio therefore reports IIII as readable but noncanonical rather than erasing the distinction.

Numbers above 3,999

There was no single universal large-number convention across Roman history. For a predictable modern digital workflow, this tool uses a vinculum convention in which an overlined symbol represents 1,000 times its base value. The underscore fallback is provided because combining overlines do not survive every plain-text system.

Dates, arithmetic and batch work

Date mode converts the numeric day, month and year components of a valid Gregorian date, with selectable order and delimiter; it is not a reconstruction of an ancient Roman calendar inscription. Roman arithmetic accepts either numbers or Roman inputs, and batch/range tools provide CSV evidence for repeated work without uploading the values.

Privacy, accuracy and limits

Conversion and export logic runs in the browser. Recent conversions use localStorage on this browser; project JSON is created only when you export it; the settings-only share link excludes conversion, date, math, batch and history content. The supported canonical numeric range is 1–3,999,999. Zero, negatives and fractional results are shown numerically rather than assigned an invented canonical Roman numeral.