Every Super Bowl has been numbered in Roman numerals since Super Bowl I in 1967 — which is why Americans in particular are used to seeing large, unfamiliar-looking numerals like LVIII (58) plastered on a stadium banner, even if they'd struggle to convert one by hand.
Seven basic symbols
I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. A number is built mostly by adding these symbols left to right: VII = 5 + 1 + 1 = 7.
The subtraction rule — and why clocks sometimes ignore it
When a symbol of lesser value precedes one of greater value, it's subtracted: IV = 5 − 1 = 4, not 6. But look closely at a traditional clock face and you'll often find IIII instead of IV for the 4 — a long-standing clockmaking convention kept for visual symmetry with VIII on the opposite side of the dial, not a mistake.
Why the system has no zero
Roman numerals were designed for counting and recording specific quantities of objects, not for abstract mathematical operations — the concept of zero as a standalone number wasn't part of that practical writing tradition.
Why you'd need this
- Working out which Star Wars-style sequel or monarch (Elizabeth II, Henry VIII) a numeral refers to.
- Formatting numbering correctly for clock faces, book preliminary pages, or outline sections.
- Testing code that converts numbers to Roman numerals against edge cases.
How numbers above 3999 were historically written
Standard notation without special marks is limited to 3999 (MMMCMXCIX), but historically, larger numbers used a line (vinculum) drawn above a symbol to multiply its value by 1000 — for example, an overlined X meant 10,000. This notation is rare and isn't part of the modern common standard, which is why Roman numeral calculators, including this one, generally don't support it.