1 = I 2 = II 3 = III 4 = IV = IIII 5 = V 6 = VI 7 = VII 8 = VIII = IIX 9 = IX = VIIII 10 = X
Roman numerals are constructed using additive and subtractive principles.
Addition is the main rule. Simply add up the digits. Example: XXI = 10+10+1 = 21.
Subtraction happens when a smaller digit comes before a larger digit. In that case, deduct the smaller digit from the larger digit. Example: IX = 10−1 = 9. The usual subtractive combinations are: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). Note that other combinations are not generally used, so 99 is not IC, but XCIX = 100−10 + 10−1 = 99.
Subtraction is a shorthand for four successive digits. Thus, IIII=IV, XXXX=XL and so on. Both forms are possible.
Use Roman numeral converter to learn how addition and subtraction work. The converter splits up a Roman numeral to its parts and teaches you how to decode it letter by letter.
Number zero does not exist in Roman numerals.
1000 = M 2000 = MM 3000 = MMM 4000 = MMMM 5000 = V 6000 = VM 7000 = VMM 8000 = VMMM 9000 = VMMMM
In order to write large numerals, one draws lines above or around numbers. This causes multiplication as per the table above.
500 = IↃ = D
There are archaic forms of Roman numbers starting from 500. The system starts with CIↃ being one thousand. Adding C and Ↄ multiplies the figure by 10. Halving the numeral (leave out the C's on the left) divides the number by 2. Thus, CCIↃↃ is 10×1000 = 10000 and IↃↃ is a half of that, 5000.
The archaic forms can be written in two alternative ways, as shown in the image below.
Use Roman numeral converter to understand modern and archaic Roman numerals. The converter shows you letter by letter what a Roman numeral is made of.
See also: Roman numerals complete list (1-3,999,999,999)