Roman Numeral Converter
Convert decimal numbers into Roman numerals or convert Roman numerals back into standard numbers.
Roman Numerals and Modern Number Conversion
A Roman Numeral Converter changes normal decimal numbers into Roman numerals and can also convert Roman numerals back into standard numbers. Roman numerals are still used in clocks, book chapters, movie sequels, outlines, monuments, event names, and decorative typography.
Roman numerals use letter symbols instead of place-value digits. The most common modern form uses I, V, X, L, C, D, and M, plus subtractive pairs such as IV, IX, XL, XC, CD, and CM. This calculator validates standard numerals from 1 to 3999.
Basic Symbols
Roman numerals are built from seven main symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. Larger numbers are formed by combining these symbols in descending order.
Subtractive Rules
Instead of writing IIII for 4, modern Roman numerals use IV. Similar subtractive pairs include IX for 9, XL for 40, XC for 90, CD for 400, and CM for 900. These rules keep numerals shorter and more standardized.
Standard Range
The common calculator range is 1 to 3999 because standard Roman numerals do not have a simple universal symbol for 5000 and above without overlines or extended notation.
Validation Helps
Many strings may look Roman but are not standard. For example, IC is sometimes guessed for 99, but the standard form is XCIX. This converter checks and normalizes the numeral form.