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2026 = MMXXVI. 1994 = MCMXCIV. Both directions, strict validation — and the subtraction rule explained so the answer makes sense.
Roman numerals still run the Super Bowl, movie copyright dates, clock faces, and monarch names — and the conversion trips everyone on the same rule: a smaller numeral BEFORE a larger one subtracts. This converter works both directions with strict validation, so VIIII comes back rejected (the correct 9 is IX) and you learn the actual standard, not just the answer.
Students and Super Bowl viewers use it: 2026 = MMXXVI, 1994 = MCMXCIV — both directions, with strict validation so VIIII doesn't pass for 9.
Add normally, subtract on inversion. Numerals run large to small and add up: MMXXVI = 1000+1000+10+10+5+1 = 2026. The exception: when a smaller numeral appears before a larger one, it subtracts — IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Two strictness rules keep notation unambiguous: never repeat a numeral four times (4 is IV, never IIII — clock faces that show IIII are a historical quirk, possibly for visual symmetry with VIII), and only I, X, and C can subtract (never V, L, or D — 95 is XCV, not VC). The subtractor also only pairs with the next two sizes up: I pairs with V and X, so 99 is XCIX, never IC.
Because M repeats at most three times, and there is no standard numeral beyond M (1,000) — MMMCMXCIX (3,999) is the ceiling of classic notation. The Romans themselves rarely needed more; when they did, they used vinculum notation (a bar over a numeral multiplying it by 1,000 — V̄ = 5,000) or apostrophus forms, neither of which survived into consistent modern use. Modern appearances respect the ceiling: Super Bowl LVIII (58), movie credits, book chapters, and outline numbering all stay comfortably under 4,000. Fun edge case: the year 1888 is the longest "modern" year to write — MDCCCLXXXVIII, 13 characters — one reason printers reportedly disliked it.
More places than you notice: Super Bowl numbering (LX in 2026), Olympic Games, monarchs and popes (Charles III, Benedict XVI), movie and TV copyright dates in end credits, book front matter and chapter headings, clock and watch faces, building cornerstones, and formal outlines (I, A, 1, a). The persistence is partly prestige — Roman numerals signal formality and permanence — and partly practical: they distinguish sequences from cardinal counts, so "Henry VIII" cannot be confused with eight Henrys. The NFL nearly dropped them for Super Bowl 50 because "L" looked weak alone, relented, and returned to numerals the next year — the closest the tradition came to retiring.