How to convert Roman numerals
- Type a number, or type Roman numerals in upper or lower case.
- Read the conversion as you type.
- If the numerals are flagged as invalid, use the suggested correct form.
- Copy the result.
The seven symbols and the subtractive rule
Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. Normally you write the largest values first and add them up, so VIII is 5 + 3 = 8 and LXX is 70.
To avoid writing four of the same symbol, a smaller numeral placed before a larger one is subtracted. Only six pairs are used in the standard form:
- IV = 4 and IX = 9
- XL = 40 and XC = 90
- CD = 400 and CM = 900
Two other rules follow from this. I, X and C can be repeated up to three times in a row, but V, L and D are never repeated and never subtracted. So 45 is XLV rather than VL, and 99 is XCIX rather than IC.
Writing years
Break the year into thousands, hundreds, tens and units, then convert each part. 2026 is 2000 + 20 + 6, which is MM + XX + VI, giving MMXXVI. 1999 is M + CM + XC + IX, giving MCMXCIX. 1984 is MCMLXXXIV.
You will see this most often in the copyright year at the end of film and TV credits, on foundation stones and on monuments. The standard form stops at 3,999 (MMMCMXCIX), because 4,000 would need a fourth M. The Romans had other ways to write larger numbers, but they are not in common use.
Why some clocks show IIII
Many clock and watch faces show four as IIII instead of IV. It is a long standing clockmaking tradition rather than a mistake, and one common explanation is that it balances the VIII on the other side of the dial. Outside clock faces, IV is the accepted form, so this converter flags IIII and suggests IV.
Questions people ask
What is 2026 in Roman numerals?
MMXXVI: MM for 2000, XX for 20 and VI for 6.
Is there a Roman numeral for zero?
No. The Roman system had no symbol for zero, so the converter starts at 1.
Why can I not convert numbers above 3,999?
Standard Roman numerals only go up to MMMCMXCIX. Larger numbers used a bar over the numeral to multiply it by 1,000, which is not part of the standard form used today.
Is IIII wrong?
In normal use, yes, four is IV. IIII is a tradition on some clock faces, which is why the tool flags it and suggests IV rather than rejecting it without explanation.
Can I type lower case numerals?
Yes. Lower case such as xiv is read the same as XIV, which helps with page numbers in the front of books.