Roman Numeral Converter

Ⅻ Enter a number or Roman numeral — the converter handles both directions automatically

Number ↔ Roman Numeral Auto-detect

Enter an Arabic number (e.g. 2026) or Roman numeral (e.g. LXIII). Prefix with _ for vinculum (e.g. _V = 5,000).

Result Enter a value above

Date Converter Date → Roman

Enter a date in numeric form (e.g. 2026/06/06). Accepted separators: – . \ / | space. Output format: YYYY/MM/DD.

Roman Date Enter a date above

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The 7 Roman Numerals

The complete set of symbols used in standard Roman numeral notation

Roman Numeral	I	V	X	L	C	D	M
Arabic Value	1	5	10	50	100	500	1,000

A Roman numeral is a system for expressing numbers that originated in the Roman Empire. It is still used today on clock faces, book chapters, film sequels, and for numbering large events such as the Olympics and the Super Bowl. Roman numerals were widely used long after the fall of the Roman Empire until Arabic numerals began replacing them around the 14th century.

Although there are only 7 Roman numerals, various rules enable them to express a wide range of numbers. Importantly, there is no zero symbol in Roman numerals — which causes some ambiguity in how they are written. There is no single universally accepted standard.

How to Read & Write Roman Numerals

Five rules that provide a framework for all Roman numeral notation

Addition — Left-to-Right

Consecutive Roman numerals are added when equivalent or when the numeral to the left is larger than the one to the right. Read from left to right, summing values as you go.

III = 3 VI = 6 MCL = 1,150 DCCLXVIII = 768

Subtraction — Smaller before Larger

When a numeral with a smaller value appears before one with a larger value, subtract the smaller from the larger. The rest of the sequence is then added normally.

IV = 5−1 = 4 XIV = 10+5−1 = 14 CD = 500−100 = 400 CDXIV = 414

III

V, L, D Cannot Be Repeated or Subtracted

The numerals V, L, and D may never be repeated. They also cannot be placed before a larger symbol, so they cannot be subtracted. For example, VX (which might imply 5) does not exist — 15 is written XV, not VX.

Maximum 3 Consecutive Repetitions

Only I, X, C, and M may be repeated, and only up to 3 times consecutively. Sequences like IIII, XXXX, or MMMM do not exist in standard notation.

III ✓IIII ✗ XXX ✓XXXX ✗ MMM ✓

Limited Subtraction Pairs

I can only precede V and X (as IV = 4, IX = 9). X can only precede L, C, or M (as XL = 40, XC = 90). C can only precede D or M. No other subtraction pairs are valid.

IV = 4IX = 9 XL = 40XC = 90 CD = 400CM = 900

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Converting Between Systems

Step-by-step methods with worked examples

Arabic → Roman Numerals

Example: Convert 768

Break the number into place-value components:

768 = 700 + 60 + 8

Convert each component from largest to smallest:

700 = DCC · 60 = LX · 8 = VIII

Combine left to right — largest to smallest value:

768 = DCCLXVIII

Roman → Arabic Numerals

Example: Convert MMMCCLXXVIII

Break into recognisable groups and sum:

MMM = 3,000 · CC = 200 LXX = 70 · VIII = 8 3,000+200+70+8 = 3,278

M̄

Large Numbers — Vinculum & Apostrophus

How Romans expressed numbers greater than 3,999

Why do large numbers need special treatment? No numeral can be repeated more than 3 times, and M is the largest symbol (= 1,000). Once we reach 3,999 (MMMCMXCIX), standard notation breaks down — the Romans developed two solutions.

The Vinculum (Overline)

A vinculum is a horizontal line written above a Roman numeral, multiplying its value by 1,000. This converter uses an underscore prefix to input vinculum numerals. The largest value this converter can represent is 3,999,999.

Input	_I	_V	_X	_L	_C	_D	_M
Roman symbol (with vinculum)	I	V	X	L	C	D	M
Arabic value	1,000	5,000	10,000	50,000	100,000	500,000	1,000,000

The Apostrophus Method

The apostrophus system uses the symbols C and Ↄ (a backwards C). Think of CↃ as a pair of parentheses encasing a value — each additional set of CↃ multiplies by 10. Each Ↄ to the right also indicates a factor of 10. Though historically significant, the vinculum is generally more straightforward for modern use.

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Dates in Roman Numeral Form

How to write and read dates using Roman numerals

There are several ways to write dates in Roman numeral form. The most common is to convert each component — day, month, and year — separately, then arrange them in the desired format (MM/DD/YYYY, DD/MM/YYYY, YYYY/MM/DD, etc.).

Example: March 4th, 2025 in YYYY/MM/DD format

2025 = MMXXV · 03 = III · 04 = IV → MMXXV/III/IV

Another common format mixes Arabic and Roman numerals — the month is written in Roman numerals while the day and year remain in Arabic. For example, March 4th, 2025 can be written as III/4/2025 or 4/III/2025.

Days of the Week

Monday	I
Tuesday	II
Wednesday	III
Thursday	IV
Friday	V
Saturday	VI
Sunday	VII

Months of the Year

January	I
February	II
March	III
April	IV
May	V
June	VI
July	VII
August	VIII
September	IX
October	X
November	XI
December	XII