Roman Numerals Converter

How Roman Numerals Work

Roman numerals are a numeral system originating in ancient Rome, using letters from the Latin alphabet to represent values. They were the standard numerical system throughout Europe until the late Middle Ages, when Arabic numerals (the 0–9 system we use today) gradually replaced them. Despite this, Roman numerals remain in widespread use today in the UK and around the world.

The system is built on seven symbols, each with a fixed value:

• I = 1 (from the Latin unus)
• V = 5 (from the shape of an open hand)
• X = 10 (two V shapes joined)
• L = 50
• C = 100 (from the Latin centum, meaning hundred)
• D = 500
• M = 1000 (from the Latin mille, meaning thousand)

Subtractive Notation Rules

The key rule that makes Roman numerals efficient is subtractive notation: when a smaller-value symbol appears immediately before a larger-value symbol, it is subtracted rather than added. This rule applies only to specific combinations:

• IV (4): I before V — 5 − 1 = 4 (not IIII)
• IX (9): I before X — 10 − 1 = 9 (not VIIII)
• XL (40): X before L — 50 − 10 = 40 (not XXXX)
• XC (90): X before C — 100 − 10 = 90 (not LXXXX)
• CD (400): C before D — 500 − 100 = 400 (not CCCC)
• CM (900): C before M — 1000 − 100 = 900 (not DCCCC)

Important rule: only one smaller numeral can be placed before a larger one as a subtractive prefix. So 8 is VIII (not IIX), and 3 is III (not IIIV).

How to Convert a Number to Roman Numerals: Step by Step

To convert any number from 1 to 3999 into Roman numerals, use the subtraction method: repeatedly subtract the largest possible Roman numeral value from the number, recording the corresponding symbol each time, until the number reaches zero.

Example: Convert 1944 to Roman numerals:

1. 1944 − 1000 (M) = 944 → write M
2. 944 − 900 (CM) = 44 → write CM
3. 44 − 40 (XL) = 4 → write XL
4. 4 − 4 (IV) = 0 → write IV
5. Result: MCMXLIV

Where Roman Numerals Are Used in the UK Today

Despite the dominance of Arabic numerals, Roman numerals retain a prominent place in British culture and formal contexts:

• Monarchy: British monarchs are numbered in Roman numerals (e.g., King Charles III, Queen Elizabeth II, Henry VIII)
• Clock faces: Traditional clock faces use Roman numerals, including Big Ben and many UK public clocks (typically using IIII for 4, not IV)
• Film & TV copyright: Release years are shown in Roman numerals in end credits (e.g., MMXXIV for 2024)
• Book prefaces: Introductory pages in books use lowercase roman numerals (i, ii, iii, iv...)
• Sporting events: The Olympic Games and other major competitions use Roman numerals (e.g., Paris 2024 was the XXXIII Summer Olympiad)
• Buildings: Many UK buildings, especially older banks and government buildings, feature Roman numeral dates in their inscriptions
• Legal documents: Certain formal legal and constitutional documents use Roman numerals for section numbering

Notable Roman Numeral Years

Frequently Asked Questions