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 XCCCXXV = 10,325.
Order X̅CCCXXV on a product
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Did you know?
Fibonacci's Sales Pitch
Fibonacci didn't invent Hindu-Arabic numerals — they originated in India around 500 AD. But his 1202 book Liber Abaci was essentially a 600-page argument that these new numbers were better for business. He showed European merchants how place value and zero could transform trade and banking. He was right. By 1500, the debate was over.
Read more →Roman Numerals: A Font for Importance
Arabic numerals are transparent: you see 42 and register the quantity instantly. Roman numerals are opaque: XLII requires a beat of translation. That friction is the feature. It forces a pause, adds formality, and signals that this number is special. Roman numerals aren't a number system anymore. They're a design language for importance.
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.