Bidirectional · Arabic ↔ Roman · Vinculum (1 to 3,999,999)
Roman Numeral Converter
Convert integers into classical Roman numerals and parse Roman numerals into Arabic decimals with detailed place value breakdowns.
Presets:
Standard base-10 Hindu-Arabic decimal representation.
Subtractive rules verified. Overline vinculum supported.
Equivalent Roman Numeral
MMXXVI
= 2,026 in Arabic decimals
Decimal Place Value Breakdown:
Thousands (1,000s)
2,000MM
Tens (10s)
20XX
Units (1s)
6VI
Roman Numerals Core Symbols Key:
I
1
V
5
X
10
L
50
C
100
D
500
M
1000
History & Rules of Roman Numeration
The Subtractive Principle
To avoid four consecutive identical letters (like IIII), the Romans placed a smaller unit before a larger one to denote subtraction:
- I precedes V (4) or X (9)
- X precedes L (40) or C (90)
- C precedes D (400) or M (900)
Letters V, L, and D are never repeated consecutively or used subtractively.
Large Numbers & Vinculum (Overline)
In classical Latin, numbers above 3,999 were recorded with a horizontal bar (a vinculum) drawn above the numeral:
An overline multiplies the symbol's base value by 1,000. For instance, V̅ = 5,000, X̅ = 10,000, and M̅ = 1,000,000.
Modern Uses of Roman Numerals
Despite the ubiquity of Arabic numerals, Roman numerals remain prominent in:
- Clock faces: Hours 1 through XII (often using IIII for aesthetic balance)
- Monarchs & Popes: King Charles III, Pope John Paul II
- Events & Media: Super Bowl LVIII, Olympics, movie copyright years