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# Roman numerals to numbers - Numbers to Roman numerals

## Convert Roman numerals into decimal numbers and vice versa

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## Roman numerals and decimal numbers

### Roman numerals

Roman numbers are a numbering system that was used in ancient Rome. This system uses letters from the Latin alphabet to represent values. The letters used in Roman numerals are I, V, X, L, C, D and M, which respectively represent the values 1, 5, 10, 50, 100, 500 and 1000. An important feature of Roman numerals is that they do not know zero and that there is no symbol for 10,000 and above.

An important concept in the Roman numbering system is subtractive notation. This is when a smaller number is placed before a larger number, meaning that you subtract the smaller number from the larger number. For example, IV means 4 (5 - 1) and IX means 9 (10 - 1).

### Decimal numbers

Decimal numbers, also known as Arabic numbers, are the numbering system most commonly used in the contemporary world. The decimal system is a positional system that uses the digits 0 through 9. It is based on the number 10, which means that each digit in a number is a multiple of a power of 10, depending on the position of the digit.

To convert Roman numerals to decimal numbers, you need to add up the values of the Roman symbols, taking into account subtractive notation. For example, the Roman numeral XVIII is converted to the decimal number 18 (10 + 5 + 1 + 1 + 1). Conversely, to convert decimal numbers to Roman numerals, you start with the largest Roman symbol that fits in the decimal number and work your way down. For example, the decimal number 18 is converted to the Roman numeral XVIII.

### Overview table

Roman numeral Decimal number
I 1
V 5
X 10
L 50
C 100
D 500
M 1000

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