Roman Numerals
Convert numbers to Roman numerals and read them back.
About this Roman numeral converter
Type a number and get the numeral; type a numeral and get the number. Both boxes update each other live, and the panel underneath breaks the answer into the pieces it is built from, so you can see exactly where each symbol came from.
Malformed numerals are caught: IIII, IC and VX are all rejected with an explanation of what the correct form would be.
The rules, in one paragraph
Seven symbols carry values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. Write them largest first and add them up. A smaller symbol placed before a larger one is subtracted instead โ but only in six specific pairings: IV, IX, XL, XC, CD and CM. I, X, C and M may repeat up to three times in a row; V, L and D never repeat at all.
Those rules together explain why 4 is IV rather than IIII, why 1999 is MCMXCIX rather than MIM, and why 45 is XLV rather than VL.
Why they stop at 3,999
Classical Roman numerals have no symbol above M and no symbol for zero, so 3,999 โ MMMCMXCIX โ is as high as standard notation goes. Larger numbers were written with a bar above a numeral to multiply it by a thousand, a convention called the vinculum, but it is not part of standard usage and does not survive plain text well.
The absence of zero is the deeper problem: Roman numerals are additive rather than positional, which makes them fine for recording a quantity and painful for arithmetic. That is why Europe eventually adopted Hindu-Arabic numerals for calculation and kept Roman ones for clock faces, book chapters, film copyright dates and Super Bowls.
Frequently asked questions
How do I write 2026 in Roman numerals?
MMXXVI โ two thousands, two tens, a five and a one. Type any year into the converter to see it broken down.
Why is 4 written IV and not IIII?
Standard notation uses subtraction for 4, 9, 40, 90, 400 and 900. IIII does appear on some clock faces by tradition, but it is not standard form.
What is the largest Roman numeral?
MMMCMXCIX, or 3,999. There is no symbol above M in standard notation, so anything larger needs the overbar convention that multiplies by a thousand.
Is there a Roman numeral for zero?
No. The system is additive rather than positional, so it never needed a placeholder. Medieval scribes wrote the word nulla when they needed to record nothing.
How do I convert a Roman numeral back to a number?
Type it into the Roman numeral box. The number appears immediately, and the panel below shows how the symbols add up.