Roman Numeral Converter

The seven symbols and the six subtractive pairs

Every standard Roman numeral is built from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. Symbols are written largest first and added together, so XVI is 10 plus 5 plus 1, or 16. To avoid four of the same letter in a row, a smaller symbol placed in front of a larger one is subtracted instead, but only in six fixed pairs. Together the 13 rows below are the whole system, and converting any number from 1 to 3999 means taking the largest row that fits, writing its symbol and repeating with what is left.

Roman numerals 1 to 100

Read across a row for consecutive numbers, or down a column to see how the tens change while the units stay the same. The units always follow the same cycle (I, II, III, IV, V, VI, VII, VIII, IX), so 41 is XL plus I, giving XLI, and 99 is XC plus IX, giving XCIX. The longest numeral under 100 is 88, LXXXVIII, at eight letters.

Hundreds and thousands

The hundreds follow the same pattern as the units and the tens, one step up: C, D and M play the parts that I, V and X play for single digits. Thousands are just repeated Ms, which is why standard form stops at 3999, MMMCMXCIX. Writing 4000 would need four Ms in a row or a fifth symbol that the standard set does not have.

Years in Roman numerals

Years are the most common reason to convert, for film and book copyright dates, anniversaries, foundation stones and tattoos. Each year is written place by place, so the breakdown column shows the exact pieces that join to make the numeral. Years from 2000 to 2099 all start with MM, which makes them shorter than most twentieth century years: 1988 is MCMLXXXVIII at 11 letters, while 2026 is MMXXVI at six.

Shortcuts that look right but are not standard form

Two rules cause almost every wrong numeral. First, a subtracted symbol can only be I, X or C, and only in front of the next two symbols up: I before V or X, X before L or C, C before D or M. So IC for 99 and IM for 999 are not allowed. Second, each place value is written on its own, so 49 is 40 plus 9, XLIX, and never one symbol taken from 50. The converter above rejects every form in the middle column and shows the standard one on the right.

These rules describe the modern standard form. Inscriptions from ancient Rome were less consistent, and additive forms such as IIII appear on many of them and on clock faces to this day.

Zero, and numbers above 3999

There is no Roman numeral for zero. The system was used for counting and recording amounts, where nothing needed no symbol, and medieval scholars who needed to write zero in tables used the Latin word nulla or just the letter N. For numbers above 3999 the usual historical device is the vinculum, a bar drawn over a numeral that multiplies it by 1000, so V with a bar is 5000 and X with a bar is 10,000. Because there is no single agreed standard and the bar cannot be typed as plain text, the converter stops at 3999. For other everyday conversions, the time duration calculator and the countdown days calculator work in the same way, with the method shown under each result.