Numbers to Roman Numerals

What are Roman Numerals?

Roman numerals are an ancient numbering system used in the Roman Empire. Based on Latin letters: I, V, X, L, C, D, M. Unlike Arabic numerals we use today, Roman numerals have an additive and subtractive notation system.

Basic Roman Numerals and Their Values

• I = 1 (Latin "unus")
• V = 5 (Latin "quinque")
• X = 10 (Latin "decem")
• L = 50 (Latin "quinquaginta")
• C = 100 (Latin "centum")
• D = 500 (Latin "quingenti")
• M = 1,000 (Latin "mille")

Roman Numeral Writing Rules

When converting decimal numbers to roman numerals, these rules apply:

• Additive principle: symbols are added together (VII = 7, where V+I+I = 5+1+1)
• Subtractive principle: smaller symbol before larger is subtracted (IV = 4, where I before V means 5-1)
• Repetition: a symbol can repeat up to 3 times in a row (III = 3, XXX = 30)
• Descending order: numerals usually arranged in descending order left to right

Common Number Conversion Examples

Here's how frequently used numbers look in Roman notation:

• 1-10: I, II, III, IV, V, VI, VII, VIII, IX, X
• Round numbers: XX (20), L (50), C (100), CD (400), D (500), CM (900), M (1,000)
• Years: MCMXC (1990), MM (2000), MMXX (2020)
• Centuries: XXI (21st century), XX (20th century), XIX (19th century)

Where Roman Numerals Are Used Today

Despite their ancient origins, Roman numerals are actively used in the modern world:

• Century numbering (20th century, 21st century)
• Monarch numbering (Elizabeth II, Louis XVI)
• Book volume and chapter numbering
• Clock faces (especially antique timepieces)
• Architectural inscriptions and monuments
• Movie numbering in series (Rocky IV, Star Wars Episode VII)
• Sporting events (Olympics XXX, Super Bowl LV)

Large Numbers Notation

For writing large numbers (over 3,999), special notations with an overline are used, meaning multiplication by 1,000. For example:

• V̄ = 5,000 (5 × 1,000)
• X̄ = 10,000 (10 × 1,000)
• L̄ = 50,000 (50 × 1,000)
• C̄ = 100,000 (100 × 1,000)
• M̄ = 1,000,000 (1,000 × 1,000)