Read Roman numerals on buildings, movies, and clocks

Copyright dates, monument years, and Super Bowl numbers use M, D, C, L, X, V, I. The rules for reading them and converting a year.

Tools used in this guide

The job

MCMLXXXIV at the end of a movie, MDCCCLXXVI on a cornerstone, LVIII on a jersey — you want the year or number without counting on your fingers.

The rules in one minute

Values are added left to right: VI = 5+1 = 6. A smaller value before a larger one subtracts: IV = 4, IX = 9, XL = 40, CM = 900. Only I, X, and C can subtract, and only once and only before the next two larger symbols.

I=1, V=5, X=10, L=50, C=100, D=500, M=1000.
2026 = MMXXVI (1000+1000+10+10+5+1). 1984 = MCMLXXXIV.
This tool is strict: IIII is rejected — the standard form is IV. Some real clocks and monuments do use IIII and other non-standard spellings; the converter answers for the canonical form.

Worked example

A movie ends with MCMXCIV. Type it in and read 1994. Type 1994 and get MCMXCIV back — the direction is detected from whether you typed digits or letters.

Limits

The standard range is 1–3999. Larger numbers exist (with overlines and other conventions) but have no single agreed short form, so they are out of scope. Zero and negatives do not exist in Roman numerals.