Roman Numeral Converter

Why IIII still ticks on some clock faces

Most people are taught that 4 is written IV, yet plenty of clock towers and wristwatches in Britain print IIII on the dial instead. Clockmakers have used both forms for centuries, and IIII on a clock face is usually put down to visual balance against the VIII opposite it, not to a mistake. Roman numerals were never fixed by a single authority, and the subtractive shorthand used today (IV, IX, XL, and so on) only settled into a firm convention long after the Romans themselves. This converter checks input against that later, standardised convention, which is also what you will find used for English regnal numbers such as Henry VIII or Elizabeth II.

The seven symbols

What this converter cannot do

Standard roman numerals have no symbol for zero and cannot express negative numbers or fractions, which is part of why they were dropped for everyday arithmetic. Without the medieval overline notation, which multiplies a numeral by 1000 by drawing a bar above it, the practical upper limit is 3999, written MMMCMXCIX. This tool sticks to that 1 to 3999 range and to standard subtractive notation only.

The formation rules

A symbol can repeat up to three times in a row, so III is 3, but a fourth I in a row is not standard notation. Subtraction is only allowed for specific pairs: I placed before V or X, X before L or C, and C before D or M. Combinations such as VX or IC break this rule and are flagged as invalid rather than silently accepted. For other number formats, try the Number Base Converter, or turn digits into written words with the Number to Words Converter.