Convert numbers to Roman numerals and back, with a symbol-by-symbol breakdown. Strict standard form, optional bracket notation for large numbers.
The symbols are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. Standard numerals run from 1 (I) to 3,999 (MMMCMXCIX). There is no zero. The numeral is built from the largest symbols that fit, using six subtractive pairs: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900. So 1994 is M + CM + XC + IV = MCMXCIV. The breakdown table lists each piece with its value, and the box under the result adds them up.
With Detect on, digits (spaces and commas are ignored, so 1,994 works) are converted to Roman, and anything with letters is converted to a number. Choose Number to Roman or Roman to number to force a direction; typing the wrong kind of input then shows a message under the box. Lower case is accepted: mcmxciv is 1994. The result always shows the numeral in upper case in its standard form.
Only the one standard way of writing each number is accepted. A symbol may repeat up to 3 times in a row, V, L and D never repeat, and only the six subtractive pairs above are allowed. So IIII (write IV), VX (a plain 5 is V), IC (write XCIX for 99), MMMM and IXI are all rejected with one fixed explanation, and the page does not repeat what you typed. A numeral that reads correctly in the wild, such as IIII on a clock face, is therefore refused here.
Standard numerals stop at 3,999. Turn on Allow large numbers and the page accepts values up to 3,999,999 using the bracket form of the overline: a numeral in brackets is multiplied by 1,000, so (V) = 5,000, (X) = 10,000, (IV)DC = 4,600 and (MMMCMXCIX)CMXCIX = 3,999,999. The part in brackets must be at least 4 (below 4,000 you write M), and the part after it must be below 1,000. The toggle is off by default, so 4000 is refused until you turn it on.
2024 is MMXXIV: MM is 2,000, XX is 20 and IV is 4. Type 2024 in the box and the table shows each piece.
The standard form writes 4 as IV, and this page accepts only the standard form so every number has exactly one numeral. IIII, VX and IC are all refused with an explanation of the rules.
3,999 in standard form (MMMCMXCIX). Turn on Allow large numbers to go up to 3,999,999, written with brackets such as (IV) for 4,000. Roman numerals have no zero, so 0 shows a message.
A numeral in brackets stands for that number times 1,000, the typed form of a line drawn over the letters. (V) is 5,000 and (MCM) is 1,900,000. Brackets are accepted only when Allow large numbers is on.
Yes. xiv, XIV and Xiv all give 14. Spaces inside a numeral are not accepted, but spaces and commas inside a number such as 1,994 are ignored.
No. It converts one whole number or one numeral at a time. Convert the day, month and year separately.