🏛️ Roman Numerals Converter
Translate between decimal numbers and Roman numerals, with validation.
Enter a decimal number (1–3999) or a Roman numeral to see the equivalent in the other format. Handy for date conversion, watchmaking, or historical references.
Roman numerals traditionally cover 1 to 3999.
Use letters I, V, X, L, C, D, M. Case insensitive.
From Decimal
Roman Numeral: MMXXIV
From Roman Numeral
Decimal: 2,024
Normalized Roman: MMXXIV
Normalized output ensures correct subtractive notation (e.g., IV, IX).
How to Use This Calculator
Enter decimal or Roman numeral
Provide a decimal number (1–3999) or type a Roman numeral using I, V, X, L, C, D, M.
Review conversions
The converter shows the corresponding representation and normalizes Roman numerals for correctness.
Copy results
Use the output in documents, watch engravings, academic work, or anywhere Roman numerals are desired.
Formula
Roman numerals use additive and subtractive combinations (e.g., IX = 9, XL = 40).
Conversion algorithm subtracts matching symbols starting from largest value to smallest.
Decimal range limited to 1–3999 due to traditional Roman numeral conventions.
Use the formula breakdown to confirm the calculation logic or perform the conversion manually if needed.
Full Description
Roman numerals appear in chapter headings, monuments, movie credits, and classic clock faces. Converting between decimal numbers and Roman numerals ensures clarity when presenting dates or enumerations in a traditional format.
This converter validates inputs, normalizes Roman numerals with subtractive notation, and provides both directions for quick referencing.
Supporting decimals beyond 3999 would require non-standard notation (overlines). For most use cases, 1–3999 covers historical and everyday needs.
Frequently Asked Questions
Why the 1–3999 range?
Traditional Roman numerals use I–M symbols. Numbers above 3,999 require additional notation (overlines), which is beyond standard usage.
Does the converter accept lowercase input?
Yes. Inputs are converted to uppercase automatically, and the normalized result uses uppercase letters.
Can I type invalid combinations like IIX?
Invalid sequences are rejected. Use proper subtractive notation (e.g., 8 is VIII, 9 is IX).
How do I convert Roman numerals with overlines?
Overline notation is not supported. For values ≥ 4,000, use decimal numbers or extend the notation manually.