Roman Numeral Converter

About Roman Numeral Converter

Roman Numeral Symbols

The seven symbols originated from tally marks, hand gestures, and early Latin abbreviations. Britannica traces most of the Roman forms back to Etruscan numerals that pre-date the Roman Republic by several centuries.

Symbol	Value	Origin
I	1	A single tally mark
V	5	A hand (five fingers) - the V shape between thumb and index finger
X	10	Two Vs, one inverted (or crossed tally marks)
L	50	Originally a symbol resembling an inverted T
C	100	From Latin "centum" (hundred)
D	500	Half of the old symbol for 1,000 (the letter split in two)
M	1,000	From Latin "mille" (thousand)

How the Conversion Works

Converting a decimal number to Roman numerals uses a greedy algorithm that subtracts the largest possible Roman value at each step, then repeats on what remains. The thirteen values used are 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, and 1 - the seven single symbols plus the six subtractive pairs CM, CD, XC, XL, IX, and IV.

Worked example: 2748. Starting at the largest symbol, 2748 minus 1000 twice leaves 748, so the result begins with MM. Next, 748 minus 500 leaves 248, giving MMD. Then 248 minus 100 twice leaves 48, so MMDCC. The 48 splits as 40 + 8, which is XL + VIII. The final result is MMDCCXLVIII. The inverse algorithm walks the string left to right, adding each symbol's value unless it sits directly before a larger one, in which case it is subtracted.

Subtractive Notation

When a smaller-value symbol appears before a larger one, it means subtraction. This avoids writing four identical symbols in a row.

Combination	Value	Instead Of
IV	4	IIII
IX	9	VIIII
XL	40	XXXX
XC	90	LXXXX
CD	400	CCCC
CM	900	DCCCC

Only I, X, and C can sit in the subtractive position, and only before the two next-larger symbols. So IV and IX are valid, but IL (49) is not - the correct form for 49 is XLIX. Per Encyclopedia Britannica, the rule is that a subtractive numeral can only precede another that is at most ten times its value, which rules out I before L or C, and V, L, or D in any subtractive role.

Worked Examples

Number	Decomposition	Roman Numeral
1776	1000 + 500 + 100 + 50 + 10 + 10 + 5 + 1	MDCCLXXVI
1994	1000 + 900 + 90 + 4	MCMXCIV
2024	1000 + 1000 + 10 + 10 + 4	MMXXIV
2026	1000 + 1000 + 10 + 10 + 5 + 1	MMXXVI
3999	1000 + 1000 + 1000 + 900 + 90 + 9	MMMCMXCIX
42	40 + 2	XLII
399	300 + 90 + 9	CCCXCIX
888	500 + 300 + 50 + 30 + 5 + 3	DCCCLXXXVIII

DCCCLXXXVIII (888) is often cited as the longest common Roman numeral in the 1-1000 range. Every symbol except M appears, which is why it shows up in textbook examples.

Rules for Valid Roman Numerals

Rule	Valid	Invalid
I, X, C, M can repeat up to 3 times	III (3), XXX (30)	IIII (use IV), XXXX (use XL)
V, L, D never repeat	V (5)	VV (use X), LL (use C)
Subtraction only with I, X, C	IV, IX, XL, XC, CD, CM	VL, LC, DM
Subtraction only before next 2 larger	IV (I before V), IX (I before X)	IL (I before L), IC (I before C)
Values must decrease left to right (except subtractive pairs)	MCMXCIV	MXM, CMCM
Only one subtractive pair per magnitude	XC (90)	XCC (can't mean 190 - use CXC)

Where Roman Numerals Are Used Today

Context	Example
Clock faces	I through XII (many still use IIII for 4 as a visual balance to VIII)
Movie and TV copyright dates	MMXXVI (2026) in end credits
Super Bowl numbering	Super Bowl LX (60) was played in February 2026
Monarchs and popes	King Charles III, Pope Francis I, Queen Elizabeth II
Building cornerstones	MCMLXII (1962) on a building facade
Book chapters and outlines	Chapter IV, Section II
Music theory	I-IV-V-I chord progressions
Academic references	Volume III, Edition IV
Legal documents and statutes	Title IX, Article II
Olympic Games numbering	Games of the XXXIII Olympiad (Paris 2024)

The Super Bowl adopted Roman numerals at Super Bowl V in 1971, in part to avoid confusion between the season year and the year the game is actually played. The NFL made one exception at Super Bowl 50, where the Arabic numeral was used for branding clarity - "L" in isolation read poorly on logos. The tradition returned for Super Bowl LI and has continued since.

Why the Limit at 3999?

Standard Roman numerals cannot represent numbers above 3999 because 4000 would require four Ms (MMMM), which violates the three-repetition rule. Historically, numbers above 3999 used a vinculum (an overline) where a bar over a symbol multiplied its value by 1000. For example, V with an overline meant 5,000 and X with an overline meant 10,000, so one million was written as M with a double bar. This notation is rarely used today, so this converter sticks to the standard 1-3999 range. Modern applications that need to number a millionth item just switch back to Arabic numerals rather than inventing Roman extensions.

There is also no Roman numeral for zero. The concept of zero as a placeholder number was not part of the Roman system and only reached Europe around the 12th century through Arabic translations of Indian mathematics. In medieval Latin texts, scribes occasionally used the word "nulla" (nothing) or the letter N to stand in for zero, but this was never formalised into the numeral system.

Common Mistakes People Make

The five most common errors in hand-written Roman numerals, based on typical feedback from classroom exercises and online quizzes:

• Writing 4 as IIII. The clock-face version exists for aesthetic reasons, but standard notation is IV.
• Subtracting across two magnitudes. Writing 99 as IC instead of XCIX. I can only precede V and X.
• Mixing case carelessly. Roman numerals are usually written in uppercase. Lowercase (mcmxciv) is acceptable in some page-numbering styles but can confuse readers.
• Combining two subtractive pairs. A number like 990 is written CMXC, not IMM or XMM - each subtractive pair handles its own order of magnitude.
• Forgetting the 3-repeat limit. 40 is XL, not XXXX. 400 is CD, not CCCC.

History in One Paragraph

The Roman numeral system was developed around 500 BC, evolving from earlier Etruscan tally marks. It served as the main numeric notation of the Roman Empire and continued to dominate European record-keeping for more than 1,500 years. Around 1300 AD, Hindu-Arabic numerals gradually replaced it for arithmetic because the new system supported place value and had a symbol for zero, which made addition, multiplication, and long calculation far easier. Roman numerals survived in contexts where readability at a glance and ceremonial style mattered more than calculation: monuments, clock faces, chapter headings, royal names, and sporting event numbering.

Years and Dates in Roman Numerals

Converting a year into Roman numerals is the single most common reason people use a converter - birthdays, anniversaries, wedding dates, and tattoo artwork all lean on them. The trick for years between 1000 and 3999 is to handle each digit of the year separately, then concatenate the pieces.

Year	Thousands	Hundreds	Tens	Units	Full numeral
1066	M	-	LX	VI	MLXVI
1492	M	CD	XC	II	MCDXCII
1945	M	CM	XL	V	MCMXLV
1999	M	CM	XC	IX	MCMXCIX
2000	MM	-	-	-	MM
2026	MM	-	XX	VI	MMXXVI

For tattoo designs, the most-requested format is a date like DD.MM.YYYY with each part as Roman numerals separated by dots. A birthday of 14 March 1990 becomes XIV.III.MCMXC. The day and month follow the same rules as any number conversion - XIV is 14, III is 3. Sticking to this rule keeps the result unambiguous and readable on skin or metal for decades.

Quick Reference: 1 to 100

Number	Roman	Number	Roman	Number	Roman
1	I	20	XX	70	LXX
2	II	25	XXV	75	LXXV
3	III	29	XXIX	80	LXXX
4	IV	30	XXX	89	LXXXIX
5	V	35	XXXV	90	XC
6	VI	40	XL	95	XCV
9	IX	44	XLIV	99	XCIX
10	X	50	L	100	C
14	XIV	60	LX	500	D
19	XIX	69	LXIX	1000	M

Related Tools

For converting numbers to English words, try the Number to Words Converter. For converting between binary, decimal, and hex, the Binary to Decimal Converter and Hex to Decimal Converter cover those bases. All conversions run in your browser.

Sources

• Encyclopedia Britannica - Roman numerals
• Wikipedia - Roman numerals (rules, history, vinculum notation)
• NBC Sports - Super Bowl LX explainer