{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"roman-numeral"},"result":{"entity_type":"calculator","id":"roman-numeral","calculator_id":"roman-numeral","canonical_url":"https://tttkmbb.com/everyday/roman-numeral","name":"Roman Numeral Converter","title":"Roman Numeral Converter – Numbers 1–3999 to Roman Numerals and Back","category":"everyday","category_name":"Everyday Life","tool_name":"convert_roman_numeral","featured_mcp_tool":false,"description":"Converts an integer from 1 to 3999 into standard (subtractive-notation) Roman numerals, or parses a Roman numeral back into a number, and shows the value of each symbol group.","use_when":"You need to write a year, chapter or clock number in Roman numerals, or read one such as MCMXCIV.","do_not_use_when":"The number is 0, negative, 4000 or larger, or not an integer (standard Roman numerals cannot express these); for other number systems use base-converter.","inputs":[{"name":"mode","label":"Direction","type":"enum","required":true,"values":[{"value":"to_roman","label":"Number → Roman numeral","aliases":["encode","to"]},{"value":"from_roman","label":"Roman numeral → number","aliases":["decode","from"]}],"description":"Conversion direction.","example":"to_roman"},{"name":"value","label":"Value","type":"string","required":true,"description":"The integer (1–3999) for to_roman, or the Roman numeral (I, V, X, L, C, D, M; case-insensitive) for from_roman.","example":"1994"}],"outputs":[{"name":"roman","label":"Roman numeral","type":"string","decimals":4,"description":"The numeral in standard form."},{"name":"number","label":"Number","type":"integer","decimals":4,"description":"The decimal value."},{"name":"breakdown","label":"Breakdown","type":"string","decimals":4,"description":"Symbol groups with their values, e.g. M (1000) + CM (900) + XC (90) + IV (4)."}],"input_schema":{"type":"object","properties":{"mode":{"description":"Conversion direction.","type":"string","enum":["to_roman","from_roman"],"examples":["to_roman"]},"value":{"description":"The integer (1–3999) for to_roman, or the Roman numeral (I, V, X, L, C, D, M; case-insensitive) for from_roman.","type":"string","examples":["1994"]}},"additionalProperties":false,"required":["mode","value"]},"output_schema":{"type":"object","properties":{"roman":{"description":"The numeral in standard form.","type":"string"},"number":{"description":"The decimal value.","type":"integer"},"breakdown":{"description":"Symbol groups with their values, e.g. M (1000) + CM (900) + XC (90) + IV (4).","type":"string"}}},"formula":"Greedy decomposition using M 1000, CM 900, D 500, CD 400, C 100, XC 90, L 50, XL 40, X 10, IX 9, V 5, IV 4, I 1; parsing accepts only the standard form M{0,3}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})","sources":[{"name":"Roman numerals (Wikipedia)","url":"https://en.wikipedia.org/wiki/Roman_numerals","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"1994 to Roman","inputs":{"mode":"to_roman","value":"1994"},"expected":{"roman":"MCMXCIV","number":1994,"breakdown":"M (1000) + CM (900) + XC (90) + IV (4)"},"url":"https://tttkmbb.com/api/v1/calculate/roman-numeral?mode=to_roman&value=1994"},{"name":"MMXXVI to number","inputs":{"mode":"from_roman","value":"MMXXVI"},"expected":{"roman":"MMXXVI","number":2026,"breakdown":"M (1000) + M (1000) + X (10) + X (10) + V (5) + I (1)"},"url":"https://tttkmbb.com/api/v1/calculate/roman-numeral?mode=from_roman&value=MMXXVI"}],"faq":[{"q":"Why is IIII or VIIII rejected?","a":"The converter accepts only standard subtractive notation (IV, IX, XL, XC, CD, CM). Additive forms such as IIII on clock faces are historical variants and are not parsed."},{"q":"How are numbers above 3999 written?","a":"With a vinculum (overline) multiplying a group by 1000, e.g. an overlined IV for 4000. This calculator supports 1–3999 only."}],"tags":["roman numerals","roman numeral converter","mcmxciv","year in roman numerals","roman to number"],"related":[{"calculator_id":"base-converter","reason":"Convert between binary, octal, decimal and hexadecimal."}],"links":{"html":"https://tttkmbb.com/everyday/roman-numeral","markdown":"https://tttkmbb.com/everyday/roman-numeral.md","json":"https://tttkmbb.com/everyday/roman-numeral.json","api":"https://tttkmbb.com/api/v1/calculate/roman-numeral","schema":"https://tttkmbb.com/api/v1/calculators/roman-numeral","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-23T23:33:40Z"}