Roman Numeral Converter

Please provide a number or Roman numeral below to convert to the other format.

Roman Numeral Date Converter

Enter a date either as Arabic digits or as Roman numerals in the field below, and the tool will switch it to the opposite notation. You may also process several values together. Accepted delimiters are hyphen, period, backslash, forward slash, vertical bar, or a blank space.

Roman numerals constitute a numeric notation devised during the Roman Empire. Today they survive in specific contexts: clock faces, chapter headings in books, and the enumeration of major spectacles like the Olympic Games and the Super Bowl.

Even after the Roman Empire collapsed, Roman numerals remained commonplace until the 14th century, when Arabic digits gradually took over. The Arabic system—what we now write daily—is the universal numeral set worldwide.

The chart below shows the 7 Roman numerals used today as well as their corresponding Roman numerals.

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

Modern usage relies on just seven Roman symbols, yet a set of conventions lets us represent many values. Typically each symbol corresponds to a power of ten, but unlike Arabic numerals there is no zero, which can cause interpretive uncertainty and prevents a single global standard. The following guidelines outline a practical approach to decoding and composing Roman numerals.

How to read and write Roman numerals

2. When Roman symbols appear side‑by‑side and each is either equal to or greater than the one that follows, you simply add their values. If a smaller symbol precedes a larger one, see rule 2 for subtraction.
   • III = 3
   • VI = 6
   • MCL = 1150
4. If a lower‑valued symbol comes before a higher‑valued one, you subtract the former from the latter. In longer sequences, once that subtraction is performed, the remaining symbols are summed in the usual way.
   • IV = 5 − 1 = 4
   • XIV = 10 + 5 − 1 = 14
   • CD = 500 − 100 = 400
   • CDXIV = 500 − 100 + 10 + 5 − 1 = 414
6. The symbols V, L, and D never appear consecutively, and they are never placed before a larger character, so subtraction with them is forbidden. Consequently combinations such as VX, LC, or DM are invalid; 15 must be expressed as XV, not VX.
8. A maximum of three identical symbols may be placed in a row—examples: III, XXX, MMM. Since V, L, and D are non‑repeatable, they are exempt from this limit. Strings like IIII, XXXX or MMMM are therefore not permitted.
9. The numeral I can only be written before (and subtracted from) V or X. Similarly, X can only be written before (and subtracted from) L, C, or M.

Large numbers

Increasingly large Roman numbers become harder to interpret and compose. Remember that a symbol may appear at most three times consecutively and that M (1000) is the highest basic symbol. Consequently, values exceeding 3999 require alternative notation. The ancient Romans devised two extensions: the apostrophus and the vinculum.

Vinculum

Roman numerals	I	V	X	L	C	D	M
Arabic numbers	1,000	5,000	10,000	50,000	100,000	500,000	1,000,000
Converter Input	_I	_V	_X	_L	_C	_D	_M

Since the vinculum multiplies a Roman numeral's value by 1,000, the largest value this converter can represent is 3,999,999.

Apostrophus method

The apostrophus method is a different system of writing Roman numerals that uses a combination of the symbols C and Ↄ. Think of CↃ as a set of parentheses encasing a number such that each additional set of CↃ indicates a factor of 10. Similarly, each Ↄ to the right of a numeral also indicates an increase by a factor of 10.

Roman numerals	IↃ	IↃↃ	IↃↃↃ	CIↃ	CCIↃↃ	CCCIↃↃↃ
Arabic numbers	500	5,000	50,000	1,000	10,000	100,000

In this system, there is no number larger than CCCIↃↃↃ. This system can be used along with the rules described above to write larger Roman numerals, though it can get a bit tricky, and using a vinculum is arguably more straightforward.

How to convert between Roman and Arabic numerals

Switching from Roman to Arabic numbers (or vice versa) requires knowing the value of each Roman symbol, as explained earlier. After grasping those rules, the conversion is simply a matter of applying them in the right order.

Converting Arabic numerals to Roman numerals

One way to convert Arabic numerals to Roman numerals is to break the numerals up into its components by place value.

Converting Roman numerals to Arabic numerals

To convert Roman numerals to Arabic numerals, sum the values of the Roman numerals.

In general, you can separate the Roman numerals by each different symbol used, but once you get more used to reading Roman numerals, you may no longer need to do this as you will be able to recognize and add the Roman numerals in your head as you go.

Dates in Roman numeral form

Roman numerals can be used to write dates in several ways. One approach is to translate each element—the day, month, and year—into Roman symbols. After choosing a date format such as MM/DD/YYYY, DD/MM/YYYY, YYYY/MM/DD, or YYYY‑MM‑DD, we reorder the converted symbols accordingly. For instance, in the YYYY/MM/DD layout, March 4^th 2025 becomes MMXXV/III/IV.

Another common style mixes Arabic and Roman figures: the month is shown in Roman numerals while the day and year stay Arabic. So the date 3/4/2025 could appear as:

III/4/2025
4/III/2025

When using this format, the year first format is not as commonly used.

Days of the week in Roman numerals

Roman numerals may also be used to represent days of the week where Monday is represented as the 1^st day of the week and Sunday is the 7^th as shown.

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

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