About the Decimal to Roman Numeral Converter
Roman numerals still appear on clock faces, in copyright dates, book chapters, monarch names and film credits. This tool converts ordinary numbers to standard Roman numerals using subtractive notation (IV for 4, IX for 9), for values from 1 to 3999, the range classical Roman numerals cover. Convert several at once, one per line.
Numbers outside 1 to 3999 are reported, since there is no standard single-symbol way to write larger values or zero. To read Roman numerals back as numbers, use Roman to Decimal.
The algorithm is greedy against a table of thirteen values: 1000 M, 900 CM, 500 D, 400 CD, 100 C, 90 XC, 50 L, 40 XL, 10 X, 9 IX, 5 V, 4 IV and 1 I. Subtract the largest value that still fits, write its letters, then repeat with what is left. 1994 peels off M, then CM, then XC, then IV, giving MCMXCIV. Because the subtractive pairs sit in the table, no letter ever needs to appear four times running.
Zero and negative numbers have no Roman form at all, and values above 3999 need the overline convention that plain text cannot show, so those inputs are reported rather than approximated. The range still covers what people actually want: a year carved on a building, a monarch, the preface pages of a book. Clock faces are the famous exception to the rules, since many of them use IIII for four purely for visual balance against the VIII opposite.
How to use
- Paste numbers from 1 to 3999, one per line.
- Copy the Roman numerals.
Common questions
- Why only up to 3999?
- Standard Roman numerals with the letters I to M reach 3999. Larger numbers need overlines, which are not plain text.
- Does it use subtractive notation?
- Yes: 4 is IV, 9 is IX, 40 is XL, and so on, the standard form.
- Can it convert a year like 2026?
- Yes, 2026 becomes MMXXVI.