Roman Numeral Converter
Convert numbers to Roman numerals and back with strict validation that explains errors like IIII or IC, plus dates and bar notation over 3,999.
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About this toolWhat is the Roman Numeral Converter?
Convert any whole number from 1 to 3,999 into Roman numerals, or type a Roman numeral to get its value. Each result is broken down symbol by symbol, so MCMXCIV is shown as M (1000) + CM (900) + XC (90) + IV (4) = 1994.
Validation is strict. Many converters quietly accept IIII, IC or VV and return a number; this one tells you why the form is not standard and what the correct numeral is. That matters when the numeral is going on a tattoo, a cornerstone, a film credit or a book chapter.
A date mode writes a full date in Roman numerals in US, European or ISO order with your choice of separator, and a switch enables the vinculum (overline) notation for numbers up to 3,999,999.
- Numbers to Roman numerals and back, 1 to 3,999
- Strict validation that explains each error
- Symbol-by-symbol breakdown of every result
- Dates in Roman numerals with order and separator options
- Optional vinculum notation up to 3,999,999
How to use the Roman Numeral Converter
- Pick a direction: Number → Roman, Roman → number, or Date → Roman.
- Type a number from 1 to 3,999, or a Roman numeral in upper or lower case. Year buttons fill in common years.
- Read the result and the breakdown of each symbol. If the numeral is not valid, the message explains the rule it breaks and suggests the standard form.
- For dates, choose the order (month, day, year or another) and a separator.
- Turn on vinculum notation for numbers over 3,999, then copy or share the result.
Worked examples
A year
Input
2026
Output
MMXXVI
MM for 2000, XX for 20 and VI for 6. Each decimal place is written separately and the pieces are joined.
Reading a numeral
Input
MCMXCIV
Output
1994
M = 1000, CM = 900, XC = 90 and IV = 4. Each pair with a smaller symbol first is subtracted.
A tempting shortcut
Input
MIM
Output
Rejected: 1999 is MCMXCIX
I can only be placed before V or X, so IM for 999 is not standard. Each decimal place must be written on its own.
A date
Input
28 October 2026, US order
Output
X.XXVIII.MMXXVI
Month 10, day 28 and year 2026 are converted separately and joined with dots.
Background and insight
Roman numerals use seven symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. A number is written from the largest value to the smallest, one decimal place at a time, and a smaller symbol placed before a larger one is subtracted. Only six subtractive pairs are used in the standard form: IV, IX, XL, XC, CD and CM.
From those rules come the checks this converter applies. I, X, C and M may repeat at most three times in a row, so 4 is IV, not IIII. V, L and D never repeat, because VV is just X. A symbol can only be subtracted from the next two symbols up, so 99 is XCIX rather than IC, and 1999 is MCMXCIX rather than MIM. The Romans themselves were less consistent, and clock faces still often show IIII for four, but the subtractive form is what is taught and expected today.
There is no zero and no standard symbol above M, so the ordinary system tops out at 3,999 (MMMCMXCIX). For larger values, medieval and later writers drew a bar (vinculum) over a numeral to multiply it by 1,000, so V̅ is 5,000 and M̅ is a million. Conventions for 4,000 vary (I̅V̅ or MV̅), and this tool uses the barred form consistently and says so.
Common use cases
Tattoos and engravings
Get a date or year right before it is permanent, with the order and separator you want.
Reading old documents
Decode copyright years at the end of film credits, building cornerstones and book prefaces.
Outlines and lists
Number sections, appendices and preliminary pages (i, ii, iii) in documents.
Events and sport
Read Super Bowl and Olympiad numbers, or monarchs and popes such as Elizabeth II and Leo XIV.
Tips and limitations
- Write each decimal place on its own: 49 is XL + IX = XLIX, not IL.
- Lower case (xlii) is read the same as upper case, and is common for page numbers.
- IIII on a clock face is a design convention, not an error in the clock, but it is not the standard form for writing numbers.
- For dates on tattoos and invitations, decide on month-day or day-month order first; 10.28 and 28.10 are both common.
- There is no Roman numeral for zero or negative numbers. Medieval writers sometimes used the word nulla.
Frequently asked questions
How do you write 2026 in Roman numerals?
2026 is MMXXVI: MM for 2000, XX for 20 and VI for 6. The year buttons above the converter fill in the current and next year as well as other common years.
Why is 4 written as IV and not IIII?
Standard Roman numerals use subtraction to avoid four repeats of a symbol, so 4 is IV and 9 is IX. IIII is still seen on many clock faces, where it is a long-standing design choice, but this converter flags it as non-standard.
What is the largest number in Roman numerals?
With the seven standard symbols the largest is 3,999, MMMCMXCIX, because M cannot repeat a fourth time. Larger numbers use a bar over a numeral to multiply it by 1,000, which this tool supports up to 3,999,999.
Is IC a valid Roman numeral for 99?
No. I can only be subtracted from V and X, the next two symbols up. 99 is written as 90 + 9, which is XC + IX = XCIX.
How do I write a date in Roman numerals?
Convert the month, day and year separately and join them with dots, dashes or spaces. 28 October 2026 is X.XXVIII.MMXXVI in month-day-year order, or XXVIII.X.MMXXVI in day-month-year order.
Is there a zero in Roman numerals?
No. The system had no symbol for zero, since it was used for counting and recording amounts. Medieval scholars computing the date of Easter sometimes wrote nulla or the letter N where a zero was needed.
Is there an in-depth guide to the Roman Numeral Converter?
Yes. “Quadratics, Scientific Notation and Roman Numerals: Writing Numbers Well” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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