Convert numbers to and from Roman numerals
Numbers above 3,999 use vinculum notation: a line above a numeral multiplies its value by 1,000.
So VCCCXXVII = 5,327.
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Cornerstones and Permanence
Walk through any old city center and you'll find Roman numerals carved into stone: MCMXXIV on a courthouse, MDCCCLXXVI on a church. A cornerstone reading "1924" looks like a label. One reading MCMXXIV looks like a declaration. The angular shapes — all straight lines, no curves — are ideal for carving and engraving, weathering centuries of rain and wind.
Read more →The Subtraction Rule: Elegant Shorthand
The subtraction rule is what makes Roman numerals clever rather than just tedious. Instead of writing IIII for 4, you write IV: "one before five." Instead of DCCCC for 900, you write CM: "one hundred before one thousand." Only six subtractive pairs exist (IV, IX, XL, XC, CD, CM), and once you know them, you can read any Roman numeral instantly.
Read more →Where do Roman numerals come from?
It is thought Roman numerals come from hand signals and tally marks. The stroke I represents a finger, the V represents the gap between thumb and fingers for five, and the X represents hands crossed for ten. The L, C, D, and M come from modifications of Greek letters like chi, theta, and phi to represent 50, 100, 500, and 1,000. Over time, these marks changed into the Latin letters people recognize today. There is no 0 in the Roman alphabet, as the concept for the number 0 didn't fully develop until India invented it around 600 CE / 10600 HE.