Roman Numeral Converter

The Formula

Roman numerals use combinations of letters from the Latin alphabet to represent numbers. The system is additive (symbols are combined and their values summed) with subtractive notation (placing a smaller value before a larger one indicates subtraction) for 4s and 9s. For example, VI = 5 + 1 = 6, while IV = 5 - 1 = 4. This subtractive convention avoids having four identical symbols in a row (IIII instead of IV). The symbols represent powers of ten (I, X, C, M) and halves of those powers (V, L, D).

Variable Definitions

How to Use This Calculator

1. 1

   Choose the conversion mode: Number to Roman, Roman to Number, or Date to Roman.

2. 2

   For Number to Roman, enter a whole number between 1 and 3999. The converter will break down each decimal place.

3. 3

   For Roman to Number, enter a valid Roman numeral (e.g., MCMXCIV for 1994).

4. 4

   For Date to Roman, enter the year, month, and day separately. Each component is converted independently.

5. 5

   Review your converted result with a complete subtractive notation breakdown showing each step.

Roman numerals use seven symbols. Subtractive notation places a smaller value before a larger one to indicate subtraction.

Understanding the Concept

Roman numerals originated in ancient Rome around 1000 BCE and remained the standard way of writing numbers throughout Europe for over a thousand years. The system uses seven letters from the Latin alphabet: I, V, X, L, C, D, and M. Numbers are formed by combining these symbols and adding their values. The subtractive notation convention (e.g., IV for 4 instead of IIII, IX for 9 instead of VIIII) was developed to prevent long strings of identical symbols and became the standard during the Middle Ages. This is why valid Roman numerals follow strict rules about placement: I can only precede V and X, X can only precede L and C, and C can only precede D and M. Symbols that represent 5s (V, L, D) are never subtracted and never repeated. Symbols representing powers of 10 (I, X, C, M) can be repeated up to three times in a row.

Frequently Asked Questions

Sources & References