This equation lets you input a Roman Numeral and get the Arabic equivalent.

This equation has input fields for selecting 16 Roman Letters, each letter can be one of the following: I, V, X, L, C, D, M.  This Roman Numeral representation is predicated on the standard subtraction convention described in the Notes Page.  For examples of Roman  Numerals following the standard subtraction conventions:

• Enter the Roman Numeral MMMMDCCCLXXXVIII, you will get the result: 4888.  This example uses only additive rules.
• Enter the Roman Numeral MCDXLIV, you will get the result: 1444:  This example uses the subtractive rules to generate the last three digits 444.
• Enter the Roman Numeral MMMMMXI, you will get the result 5011.

This equation will let you write a Roman Letter sequence that does not conform to the additive/subtractive conventions most commonly used and outlined in the Notes Page.

Note that many of the Roman Letter sequences that can be translated here, while not following the standard additive/subtractive convention, do represent Roman Numerals found in historical documents of the Roman era.  In other words, the Romans themselves did not always follow Roman Numeral conventions.

Notes

 Basics of Roman Numerals ==

A numeric value is represented in Roman Numeral notation as a combination of letters, generally capitalized.  The letter used, in order of magnitude are I, V, X, L, C D M, representing respectively: 1, 5, 10, 50, 100, 500, 1000.  Roman Numerals are written with the letters representing largest values starting on the left and letters of decreasing value in sequence to the right -- with exceptions for subtractive notation rules outlined below.  As a simple example the number 155 would be written CLV, with C on the left of the Roman Numeral being the largest numeric value represented by a letter and the V being the smallest value represented on the right.

There is no zero in the Roman Numeral system.

Additive Notation

Each letter in Roman Numeral is added together, with the exceptions defined for Subtractive Notation.  So, LVII represents 50 + 5 + 1 +1 = 57.

Subtractive Notation

A small set of additional rules are used to avoid repeating the roman letters more than three times.  So, for example, any instance of 4 or 9 is written with a subtracted value preceding a larger value.  Here are key examples of the subtraction notation for Roman Numerals:

    The number 4 is written as IV (not as IIII).
     The number 9 is written as IX (not as VIIII).
     The number 40 is written as XL (not as XXXX).
     The number 90 is written as XC (not as LXXXX)
     The number 400 is written as CD (not as CCCC)
     The number 900 is written as CM (not as DCCCC)

Counting in Roman Numerals

The integer number through 25 in Roman Numerals are as follows:

Using the Equation

The input fields for this equation allow you to choose a letter for each of the sixteen input fields. Following the Roman Numeral convention for writing the largest to smallest value letters  left to right, an example number 1,111 would be written MCXI. The exceptions to the largest value letters being ordered left-to-right is explained in the Subtractive Notation subsection above.