Conversor de números romanos
Convierte números a números romanos y números romanos a cifras, con las reglas sustractivas explicadas y el desglose de cada símbolo.
Cómo usar esta calculadora
- 1Choose which direction you are converting.
- 2Enter a whole number from 1 to 3999, or a Roman numeral using only I, V, X, L, C, D, and M.
- 3The symbol breakdown shows how the numeral is built place value by place value.
Cómo funciona
Reglas de los números romanos
I = 1 V = 5 X = 10 L = 50 C = 100 D = 500 M = 1000 Repite un símbolo hasta tres veces para sumar: III = 3 Coloca un símbolo menor antes de uno mayor para restar: IV = 4 Solo IV, IX, XL, XC, CD, CM son pares sustractivos válidos
Los números romanos combinan siete símbolos (I, V, X, L, C, D, M) sumando sus valores de mayor a menor. Un símbolo menor colocado antes de uno mayor se resta, lo que da las formas como IV (4) o IX (9). Solo se permiten seis pares sustractivos y ningún símbolo se repite más de tres veces seguidas.
Ejemplo resuelto
El año 2024 se escribe MMXXIV: MM = 2000, XX = 20 y IV = 4. A la inversa, XLII se lee como XL (40) + II (2) = 42.
Conversor de números romanos: la guía completa
How to read a Roman numeral
Work left to right and compare each symbol with the one after it. If it is larger than or equal to the next, add it. If it is smaller, subtract it. MCMXCIV reads as M (1000), then C before M meaning −100 +1000 = 900, then X before C meaning 90, then I before V meaning 4 — giving 1994.
Because the subtractive pairs are always exactly two symbols, you never need to look more than one symbol ahead. That is what makes the system readable at all despite having no positional notation.
The rules that make a numeral valid
Only I, X, and C may be subtracted, and only from the next two larger symbols. That gives exactly six legal subtractive pairs: IV, IX, XL, XC, CD, CM. V, L, and D are never subtracted, and never repeated — VV would simply be X.
A symbol repeats at most three times in a row. Four of anything triggers the subtractive form instead. This is why IIII is non-standard, even though clock faces have used it for centuries for visual balance against the VIII opposite.
This calculator enforces canonical form by converting your input back to a numeral and checking it matches. IC, VX, and IIII are all rejected rather than silently interpreted, which is what you want when checking a copyright date or a monument inscription.
Why there is no zero and no numbers past 3999
Roman numerals are a tally system, not a positional one. Each symbol carries its own fixed value regardless of where it sits, so there is no empty place to mark and therefore no need for a zero. That absence made arithmetic painful and is a large part of why Hindu-Arabic numerals displaced them for calculation.
M is the largest standard symbol, and no more than three may repeat, so MMMCMXCIX (3999) is the ceiling. The Romans extended the system with a vinculum — a bar over a symbol multiplying it by 1,000, so V̄ meant 5,000 — but overbars do not survive plain text, which is why virtually every converter stops at 3999.
Where you still see them
Film copyright dates, book chapter numbers, monarch and pope regnal numbers, Super Bowl editions, clock faces, and the outline levels of formal documents. In each case the numerals signal formality or tradition rather than serving any computational purpose.
The most practical use today is decoding a copyright line at the end of a film: MCMLXXXIV is 1984, MMXIV is 2014. Paste it into the converter above rather than counting Xs.
Preguntas frecuentes
¿Cómo funciona la regla sustractiva?
Cuando un símbolo de menor valor va antes de uno mayor, se resta en lugar de sumarse. Así, IV es 5 − 1 = 4 y IX es 10 − 1 = 9. Solo son válidos seis pares: IV, IX, XL, XC, CD y CM.
¿Cuál es el número romano más grande?
Con los símbolos estándar, el mayor es MMMCMXCIX = 3999. Para números más grandes, los romanos usaban una barra sobre el símbolo (el vínculo) que multiplicaba su valor por mil, algo que no puede escribirse en texto normal.
¿Existe el cero en los números romanos?
No. El sistema romano no tiene símbolo para el cero ni para los números negativos; se ideó para contar cantidades. El concepto del cero llegó mucho después, con el sistema de numeración indoarábigo que usamos hoy.