Why is 4 written IV and not IIII?

The subtractive principle is used to avoid four consecutive identical symbols. Placing a smaller value before a larger one means subtraction: IV = 5 - 1 = 4. This rule applies to I before V and X, X before L and C, and C before D and M. Note that some clock faces still use IIII for aesthetic balance — that is an accepted stylistic exception, not the standard.

What is the largest Roman numeral this tool supports?

With vinculum notation (overlines) enabled, this tool converts up to 3,999,999. Without vinculum, the maximum is 3,999 (MMMCMXCIX). In classical Roman numeral usage the practical limit was around 3,999, but the vinculum convention extended the system by multiplying overlined symbols by 1,000.

Is there a Roman numeral for zero?

No. The Roman numeral system has no symbol for zero. The Latin word "nulla" (meaning "none") was used in its place. Zero as a numeric concept with its own symbol was developed independently in India and later introduced to Europe through Arabic mathematics — which is why our standard digits are called Arabic numerals.

Why do some clocks use IIII instead of IV for 4?

Several reasons have been proposed: visual symmetry on the clock face (IIII mirrors VIII on the opposite side), the historical preference of certain royal patrons, easier reading at a glance, and simpler manufacturing of clock dies. Either form is considered acceptable on clock faces, though IV is the standard in all other contexts.

Roman Numeral Converter

Name: Roman Numeral Converter
Availability: InStock
Author: Nham Vu

Enter an Arabic number (1–3,999,999) to get its Roman numeral, or type a Roman numeral to convert it back. Enable vinculum mode for numbers above 3,999.

Number to Roman

1 – 3,999,999

Arabic number

Use vinculum notation (overlines for 4,000+)

Quick:

Enter a number above to see its Roman numeral.

Roman to Number

Case-insensitive

Roman numeral

Enter a Roman numeral above to convert it.

Character highlighting:

M Valid symbol ? Invalid character

Standard symbols and their values. The subtractive combinations below are used to avoid four consecutive identical symbols.

Basic Symbols

Symbol	Value
M	1,000
D	500
C	100
L	50
X	10
V	5
I	1

Subtractive Combinations

Symbol	Value
CM	900
CD	400
XC	90
XL	40
IX	9
IV	4

Vinculum (overline) Symbols

Symbol	Value
M	1,000,000
D	500,000
C	100,000
L	50,000
X	10,000
V	5,000

Summary