Sumivo · Mathematics
Roman Numeral Converter
Convert between numbers and standard Roman numerals in either direction. Enter a number from 1 to 3999 to get its Roman form, or a Roman numeral to read it as a number — with the symbol-by-symbol breakdown.
01 / inputs
02 / result
ROMAN NUMERAL
MMXXIV
- Number
- 2024
- Roman numeral
- MMXXIV
- Symbols used
- M + M + X + X + IV
- Symbol count
- 5
Calculation trace
- 2024 = M=1000 + M=1000 + X=10 + X=10 + IV=4Break 2024 into standard Roman pieces, largest first
- 2024 = MMXXIVJoin the symbols in order
How it works
Roman numerals build a value from seven symbols — I=1, V=5, X=10, L=50, C=100, D=500 and M=1000 — read from left to right and mostly added together. The one twist is subtractive notation: when a smaller symbol sits directly before a larger one, it is subtracted, which is why IV is 4 (5−1) and XC is 90 (100−10). Only six such pairs are standard: IV, IX, XL, XC, CD and CM. To turn a number into Roman, the tool takes the largest symbol or pair that fits, subtracts it, and repeats — so 1994 becomes M + CM + XC + IV = MCMXCIV. To read a Roman numeral, it adds each symbol (subtracting where a smaller one precedes a larger one) and then checks the spelling is the standard one, so a non-standard form such as IIII or IC is flagged rather than silently accepted.
Assumptions & limits
- Whole numbers from 1 to 3999 only. There is no Roman symbol for zero, and values of 4000 and above need an overbar (vinculum) that is outside standard notation.
- Only the six standard subtractive pairs are accepted: IV, IX, XL, XC, CD and CM.
- Roman input is case-insensitive and surrounding spaces are ignored; a number made of the digits 0–9 is converted to Roman instead.
- A value has exactly one standard spelling, so non-standard forms such as IIII, VV or IC are rejected with the correct spelling shown.
FAQ
- What is the largest number I can write?
- Standard Roman numerals go up to 3999, written MMMCMXCIX. Larger values historically used an overbar to multiply a symbol by 1000, which is non-standard and not supported here.
- Why is 4 written IV and not IIII?
- Standard notation uses the subtractive pair IV (5−1) for 4. IIII does appear on some clock faces, but it is not the standard spelling, so the converter treats IV as correct and flags IIII.
- Is there a Roman numeral for zero?
- No. The Roman system has no symbol for zero, which is why the converter starts at 1.
- Why is IC rejected for 99?
- Subtraction is only allowed between the six standard pairs, and I can only be placed before V or X. 99 is written XCIX (90 + 9), so IC is flagged as non-standard.
- Can I convert a Roman numeral back to a number?
- Yes — enter a Roman numeral such as MCMXCIV and the tool reads it as 1994, showing how each symbol adds up. It works in both directions automatically based on what you type.
Related calculators
SOURCES
- Encyclopædia BritannicaRoman numeral ↗
The seven Roman symbols (I, V, X, L, C, D, M), subtractive notation (IV, IX, XL, XC, CD, CM) and the standard 1–3999 range
Accessed 2026-09-29