Roman Numerals Converter: Decimal to Roman

Read and write standard Roman numerals

Type in either field to convert positive integers from 1 to 3,999. The other field updates immediately. Lowercase Roman letters and surrounding spaces are accepted; the result uses uppercase letters. The visible breakdown groups thousands, hundreds, tens and units using the same accepted subtraction pairs as the converter.

Worked examples and accepted forms

Enter 2026 to obtain MMXXVI: MM (2,000) + XX (20) + V (5) + I (1). Enter mcmxciv to obtain 1994: M (1,000) + CM (900) + XC (90) + IV (4). The upper boundary, 3999, becomes MMMCMXCIX.

The seven letters are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. This tool accepts six subtraction pairs: IV, IX, XL, XC, CD and CM. It checks the full numeral sequence rather than subtracting any smaller letter from a larger one. IL, IIV and VX are rejected.

Why a familiar inscription may be rejected

Some clock faces use IIII for four. This converter uses IV and rejects IIII; that is a convention of this tool, rather than a judgement about every historical inscription. Overlines, Unicode numeral glyphs such as Ⅳ, fractions, zero and negative values are outside its supported input. Type IV instead of the single Roman numeral character.

If XQ is entered, the tool keeps the input visible and reports an error; it does not silently turn XQ into X. Invalid input clears the opposite field and hides both copy buttons. Clear Fields empties both sides. There is no direction toggle or optional Show Steps control: the two editable fields and breakdown are always available for a valid result.

Using the result in a document

Use Copy Roman for labels or chapter numbers and Copy integer when you need the decimal value. Check the target document's numbering convention before replacing an inscription. The converter changes notation; it does not perform arithmetic on Roman expressions or interpret archaeological dates.

Processing and privacy

Conversion and validation run in browser memory without a calculation API or saved conversion history. Reloading clears the inputs. Copy writes to the device clipboard. General site analytics are covered by the Privacy Policy. For binary and hexadecimal integers, use the number-base converter.