Roman Numerals Converter — Arabic to Roman & Back

Guide

About Roman Numerals

Convert between Arabic and Roman numerals — 1 to 3,999,999. Numbers above 3,999 use vinculum (overline) notation to multiply by 1,000. Useful for copyright years, movie sequels, sports championships, and any time you need to encode a number with the weight of antiquity.

The seven symbols

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

Subtractive pairs

IV (4), IX (9)
XL (40), XC (90)
CD (400), CM (900)

Common workflows

Movie sequel year. Rocky IV (4) — IV. Star Wars Episode IX (9) — IX.

Copyright year. © MMXXV — 2025.

Super Bowl. Super Bowl LVIII — 58. Super Bowl LX — 60.

Outline numbering. Top-level Roman, sub-level letter, sub-sub Arabic. The tool pins the conversion.

Why Romans don’t add up

The numeral system is positional only loosely (subtractive notation breaks pure positional). Adding two Roman numerals is harder than adding two Arabic-Indian numerals — and that is exactly why the world switched to Arabic-Indian. Roman numerals survive as decoration; Arabic-Indian rules math.

Frequently asked questions

Which year is MMXXV?

2025. M = 1000, X = 10, V = 5 — so M+M+X+X+V = 2025.

Why do some numbers use subtraction?

To avoid four-in-a-row. 4 is IV (5 minus 1), not IIII. 9 is IX. 40 is XL. 90 is XC. 400 is CD. 900 is CM.

How to write 4,000?

Above 3,999, classical Roman numerals run out. We use vinculum (overline) — I̅V̅ means 4 × 1,000 = 4,000. Or you can switch to mixed Arabic/Roman.

Romans never had a zero?

Correct. Their math was concrete, not symbolic. Zero entered European math through Arabic-Indian numerals around the 12th century.

Can clocks have IIII for 4?

Yes — clock faces traditionally use IIII for 4 (visual balance with VIII for 8). Both forms are accepted; the tool defaults to IV but offers a toggle.

Performance for big numbers?

Up to 3,999,999 cleanly. Above that, the vinculum gets unwieldy.

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Last updated: 2025-01-15