Roman Numeral to Decimal Converter
Convert Roman numerals (I, V, X, L, C, D, M) to decimal numbers instantly
Example: XII, IX, CXL
➡️
Range: 1 to 3999
Conversion Result
XII = 12
Twelve • 1 Dozen • 1 Foot
📚 Roman Numeral Conversion Details
Roman Numeral Symbols
I = 1, V = 5, X = 10
L = 50, C = 100
D = 500, M = 1000
L = 50, C = 100
D = 500, M = 1000
Seven basic symbols form all Roman numerals.
Subtraction Rule
IV = 4 (5-1)
IX = 9 (10-1)
XL = 40 (50-10)
XC = 90 (100-10)
IX = 9 (10-1)
XL = 40 (50-10)
XC = 90 (100-10)
A smaller numeral before a larger one means subtraction.
Addition Rule
VI = 6 (5+1)
XII = 12 (10+1+1)
LX = 60 (50+10)
DCC = 700 (500+100+100)
XII = 12 (10+1+1)
LX = 60 (50+10)
DCC = 700 (500+100+100)
A smaller numeral after a larger one means addition.
Common Uses
- Book chapters
- Movie copyright years
- Monarch names
- Clock faces
- Building cornerstones
📏 How Roman Numerals Work
Roman numerals use a combination of seven letters to represent numbers:
- Basic Symbols: I (1), V (5), X (10), L (50), C (100), D (500), M (1000)
- Addition: When smaller values follow larger values, add them (e.g., VI = 5 + 1 = 6)
- Subtraction: When smaller values precede larger values, subtract them (e.g., IV = 5 - 1 = 4)
- No Zero: Roman numerals don't have a symbol for zero
- Maximum Value: Standard Roman numerals go up to 3,999 (MMMCMXCIX)
// Roman to Decimal Conversion Algorithm:
1. Map each symbol to its value
2. Read from left to right
3. If current symbol < next symbol: subtract
4. Else: add
// Example: XIV
X = 10 (current < I? No) → 10
I = 1 (current < V? Yes) → 1 - ?
V = 5 → Result: 10 + (5-1) = 14
1. Map each symbol to its value
2. Read from left to right
3. If current symbol < next symbol: subtract
4. Else: add
// Example: XIV
X = 10 (current < I? No) → 10
I = 1 (current < V? Yes) → 1 - ?
V = 5 → Result: 10 + (5-1) = 14
📊 Common Roman Numerals
| Roman | Decimal | Name |
|---|---|---|
| I | 1 | One |
| IV | 4 | Four |
| V | 5 | Five |
| IX | 9 | Nine |
| X | 10 | Ten |
| L | 50 | Fifty |
| C | 100 | One Hundred |
| D | 500 | Five Hundred |
| M | 1000 | One Thousand |
❓ Frequently Asked Questions
Q: What is the largest Roman numeral this converter handles?
A: This converter handles numbers up to 3,999 (MMMCMXCIX).
Q: Why is 4 written as IV instead of IIII?
A: IV follows the subtraction rule (5-1). While IIII is sometimes used on clock faces, IV is the standard form.
Q: Can Roman numerals represent zero?
A: No, the Roman numeral system has no symbol for zero.
Q: How do you write years in Roman numerals?
A: Years are written by combining symbols. Example: 2024 = MMXXIV (1000+1000+10+10+4).