Roman Numerals

Convert numbers and dates to Roman numerals and back, with how each one is built

Number, Roman numeral or date

Lowercase (i, ii, iii, as in page numbers)

How they work

100

500

1,000

The symbols add up from the largest to the smallest: MDCLXVI is 1,666. A symbol placed before a larger one is subtracted instead: IV is 4, IX 9, XL 40, XC 90, CD 400, CM 900. A symbol repeats at most three times, so 4 is IV, not IIII (though many clock faces show IIII). There is no zero. Above 3,999, a bar over a numeral multiplies it by 1,000: V̅ is 5,000.