Roman Numeral Converter

Roman numerals are the number system of ancient Rome. They use letters instead of digits, and they are still used today for clock faces, book chapters, film sequels, the names of kings and queens, and the year on old buildings. The Roman Numeral Converter changes a number into a Roman numeral and back, and it can write a date in Roman numerals.

What you enter

• A number from 1 to 3,999, to get its Roman numeral.
• A Roman numeral, to get its value. Lower case letters are accepted.
• A day, a month and a year, to write a date in Roman numerals, with dots, hyphens or slashes between the parts.

The seven symbols

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

The rules

• Add from left to right. Symbols are written from the largest to the smallest, and their values are added. VIII is 5 + 1 + 1 + 1 = 8.
• Repeat a symbol up to three times. III is 3, and XXX is 30. The number 4 is not IIII, but IV.
• A smaller symbol in front of a larger one is taken away. IV is 5 - 1 = 4, and XL is 50 - 10 = 40.
• Only I, X and C can be taken away, and only from the next two larger symbols. So there are six pairs: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900).
• V, L and D are never repeated, and they are never taken away.

How a number is turned into a numeral

The calculator takes the number one place at a time, from the thousands to the ones, and writes each part with the symbols. Take 2026:

Place	Part of the number	Roman numeral
Thousands	2000	MM
Hundreds	0	(nothing)
Tens	20	XX
Ones	6	VI

Put together, 2026 is MMXXVI. The digits 1 to 9 in each place follow the same pattern:

Digit	Ones	Tens	Hundreds	Thousands
1	I	X	C	M
2	II	XX	CC	MM
3	III	XXX	CCC	MMM
4	IV	XL	CD
5	V	L	D
6	VI	LX	DC
7	VII	LXX	DCC
8	VIII	LXXX	DCCC
9	IX	XC	CM

How a numeral is turned into a number

Read from left to right. If a symbol is smaller than the one after it, take it away. Otherwise, add it. For MCMXCIV:

Part	Value
M	1,000
CM (1,000 - 100)	900
XC (100 - 10)	90
IV (5 - 1)	4
Total	1,994

█████████████████████████████████████████
M 1000            CM 900           XC 90 IV 4

The bar shows how the 1,994 is divided between the parts. Each block is about 50 units.

Some examples

• Number: 4
  Roman numeral: IV
  Why: 5 - 1
• Number: 9
  Roman numeral: IX
  Why: 10 - 1
• Number: 14
  Roman numeral: XIV
  Why: 10 + (5 - 1)
• Number: 49
  Roman numeral: XLIX
  Why: (50 - 10) + (10 - 1). It is not IL.
• Number: 99
  Roman numeral: XCIX
  Why: (100 - 10) + (10 - 1). It is not IC.
• Number: 444
  Roman numeral: CDXLIV
  Why: (500 - 100) + (50 - 10) + (5 - 1)
• Number: 1994
  Roman numeral: MCMXCIV
  Why: 1000 + 900 + 90 + 4
• Number: 2026
  Roman numeral: MMXXVI
  Why: 2000 + 20 + 6
• Number: 3999
  Roman numeral: MMMCMXCIX
  Why: The largest standard numeral

Chart: how long is the numeral?

Each numeral is drawn with two blocks for each letter. Green is short, amber is longer, and red is the longest of all.

4     IV                ████ 2 letters
8     VIII              ████████ 4 letters
49    XLIX              ████████ 4 letters
444   CDXLIV            ████████████ 6 letters
2026  MMXXVI            ████████████ 6 letters
38    XXXVIII           ██████████████ 7 letters
1994  MCMXCIV           ██████████████ 7 letters
88    LXXXVIII          ████████████████ 8 letters
3888  MMMDCCCLXXXVIII   ██████████████████████████████ 15 letters

3888 needs the most letters of all the numbers from 1 to 3,999, with 15. A number does not have to be large to have a long numeral. 88 needs 8 letters, and 2000 needs only 2.

What the converter checks

Not every combination of letters is a valid numeral. The converter accepts only the standard form. If you enter something else, it tells you what you probably meant:

• You enter: IIII
  Problem: A symbol is repeated four times
  Correct form: IV (4)
• You enter: IC
  Problem: I can only be taken away from V and X
  Correct form: XCIX (99)
• You enter: VX
  Problem: V is never taken away
  Correct form: V (5)
• You enter: MMMM
  Problem: More than three thousands
  Correct form: Out of range

The number 4 is written IIII on many clock faces. This is an old custom, and it is accepted on clocks, but it is not the standard form for other uses.

Writing a date in Roman numerals

To write a date, each part is changed on its own: the day, the month and the year. The 24th of September 2026 is:

Part	Number	Roman numeral
Day	24	XXIV
Month	9	IX
Year	2026	MMXXVI
Together		XXIV.IX.MMXXVI

The calculator checks that the date exists. The 29th of February is accepted in 2024, but not in 2023. This is popular for weddings, tattoos, engraved gifts and the dates of buildings.

Where Roman numerals are used

• Clock faces, and the hours on watches.
• Names of monarchs and popes, such as Elizabeth II.
• Sequels and events, such as Super Bowl LVIII, which is 58.
• Outlines and lists, book chapters, and the pages at the front of a book.
• Years of copyright in the credits of films and television shows.

Why the largest number is 3,999

The Romans had no symbol for 5,000 or more. To write bigger numbers, they put a bar over a numeral, which multiplied it by 1,000. So V with a bar is 5,000. A bar over a letter cannot be typed in a simple box, so the converter works up to MMMCMXCIX, which is 3,999. The Romans also had no symbol for zero.

Tips

• Work from the left, one place at a time. This is the easiest way to write a number by hand.
• Remember the six pairs: IV, IX, XL, XC, CD and CM.
• Check a numeral by adding it up again.

What this converter does not include

• Numbers above 3,999, fractions and zero.
• Old or unusual forms, such as IIII on a clock, or IIX for 8, which some ancient inscriptions used.
• The bar over a numeral, which cannot be typed here.

This tool gives a general conversion in the standard modern form of Roman numerals.