Roman Numeral Converter
Type a number or a Roman numeral – the converter detects the direction automatically, shows every step and explains what is wrong with invalid forms like IIII or IC, with the correct spelling.
How it is calculated
The seven Roman numeral symbols
| Symbol | I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|---|
| Value | 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
Roman numerals are read left to right and added up, with symbols written from largest to smallest: MDCLXVI = 1000 + 500 + 100 + 50 + 10 + 5 + 1 = 1666.
How to convert Roman numerals
- Type a number from 1 to 3,999 or a Roman numeral such as MMXXVI.
- The converter detects the direction by itself.
- Read the result and the steps – for invalid forms like IIII the correct form is shown.
The subtractive rule
A smaller symbol placed before a larger one is subtracted. Standard modern notation uses exactly six such pairs:
| Pair | Calculation | Value |
|---|---|---|
| IV | 5 − 1 | 4 |
| IX | 10 − 1 | 9 |
| XL | 50 − 10 | 40 |
| XC | 100 − 10 | 90 |
| CD | 500 − 100 | 400 |
| CM | 1000 − 100 | 900 |
This gives the rules the converter checks:
- Only I, X and C can be subtracted, and only from the next two larger symbols. IC for 99 is wrong – it is XCIX; 49 is XLIX, not IL.
- V, L and D are never subtracted (VX is invalid) and appear at most once (VV is X).
- No more than three identical symbols in a row: 4 is IV, not IIII.
- Only one smaller symbol may precede a larger one: 8 is VIII, not IIX.
Number → Roman numeral, place by place
Split the number into thousands, hundreds, tens and ones, convert each place separately and join the parts. Zeros are simply left out.
Example 1994: 1994 = 1000 + 900 + 90 + 4 → M + CM + XC + IV = MCMXCIV.
Example 2026: 2026 = 2000 + 20 + 6 → MM + XX + VI = MMXXVI.
Roman numeral → number
Read from the left: if a symbol is smaller than the one to its right, subtract it; otherwise add it. MCMXCIV = 1000 + (1000 − 100) + (100 − 10) + (5 − 1) = 1000 + 900 + 90 + 4 = 1994.
Why only up to 3,999?
Because M may appear at most three times, MMMCMXCIX = 3,999 is the largest number in standard form. Larger values used extra marks such as a bar over the numeral (×1,000), which are not used consistently today. There is no zero.
More about numbers: binary and hex with the number base converter, mental maths with times tables practice, and fractions with the fraction calculator.
Frequently asked questions
How do you write 2026 in Roman numerals?
2026 = 2000 + 20 + 6 = MM + XX + VI, so MMXXVI. Thousands, tens and ones are converted separately; the hundreds digit is 0 and is left out.
Why is 4 written IV and not IIII?
In standard form no symbol is repeated more than three times, so 4 and 9 use the subtractive rule: IV = 5 − 1, IX = 10 − 1. Some clock faces traditionally still show IIII.
Is IC a correct way to write 99?
No. I may only precede V and X, X only L and C, and C only D and M. 99 = 90 + 9 = XC + IX = XCIX.
What is the largest Roman numeral?
In standard form it is 3,999 = MMMCMXCIX, since M may appear at most three times. Larger numbers need extra marks such as an overline (V̅ = 5,000).
Is there a Roman numeral for zero?
No, Roman numerals have no symbol for zero. Empty places, like the hundreds in 2026, are simply omitted.
How do I read a year in Roman numerals?
Work left to right in groups: MCMLXXXIV = M (1000) + CM (900) + LXXX (80) + IV (4) = 1984. The converter shows these steps for every input.
Sources and legal basis
As of:
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