Easy Ways to Convert Roman Numerals

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Easy Ways to Convert Roman Numerals

As the name suggests, Roman Numerals were started in ancient Rome, around 900 – 800 BC. They are a set of seven basic symbols that transformed into numerous letters we use now.

This article will cover the history of Roman numerals, their applications, easy ways to convert Roman numerals to numbers, and a description of basic Roman numerals converter charts.

III Numerals

In ancient Rome, the roman numerals came around as a basic need to count the objects regarding the trade and communications between people. Counting numbers on fingers wasn’t possible and functional for trading and exchange between people; that’s how Roman numerals were discovered.

The seven basic symbols for Roman Numerals are I, V, X, L, C, D, and M, which represent 1, 5, 10, 50, 100, 500, and 1000, respectively. A single line ‘I’ represents one finger or one unit, ‘V’ is a sign formed by two fingers representing five units, and ‘X’ is two hands crossing each other, representing ten units. 

‘M’ originates from the Greek letter ‘Φ’ called phi. It represents 1000 in the Hindu-Arabic numeral system. It used to be represented by C, I and C backwards, for example, ‘CIƆ’.

‘D’ represents 500 values which is half of 1000 (M). It was used to be represented by the symbol ‘IƆ’, which is half of the symbol ‘CIƆ’.

‘C’ represents 100. It was originally represented by the symbol theta – Θ.

‘L’ represents the value 50. It used to be represented by the letter psi – Ψ, which on flattening will look like an inverted T. It also used to be represented by ‘I’ and ‘V’.

The primary key to identifying the Roman numerals is when the symbol of a greater value is placed after the symbol of lesser value, then the value is added. For example, if ‘X’ is placed after ‘L’, then the value of the symbol ‘LX’ becomes 60 (50 10). 

If the symbol of equal value is placed after, then also the value is added. For example, if ‘I’ is placed after ‘I’, then the value of the symbol ‘II’ becomes 2 (1 1). If the symbol of lesser value is placed before the symbol of the greater value, then the value gets subtracted. For example, if the symbol ‘C’ is placed before ‘D’, then the symbol’s value becomes 400 (-100 500).

The below table will give an idea of the representation of the Roman numerals and their corresponding numbers:

Roman numerals Numbers
I 1
IV 4
V 5
IX 9
X 10
XL 40
L 50
XC 90
C 100
CD 400
D 500
CM 900
M 1000

How to Convert Roman Numerals to Numbers 

Steps to convert Roman numerals to numbers:

  1. The fundamental symbols I, V, X, L, C, D, and M are used as basics in the whole Roman numerals system.
  1. The Roman numeral symbol of equal value is placed side by side to indicate addition. For example, the value of ‘III’ is 1 1 1. 
  1. Another rule is not to add any symbol more than three times. For example, the symbol for 4 cannot be represented by ‘IIII’. In this case, the smaller numeral is placed before the next bigger numeral, which is ‘V’. The Roman to represent value 4 will be ‘IV’ ( -1 5).
  1. Another point is that only one value can be subtracted from the bigger Roman numeral.
  1. Let’s take the example of 719 and 718. To begin converting this number to Roman numerals, we must identify the closest symbol to the number, that is 500 (D). We now have two 100s left, and 100 is represented by C. So, we can write 700 as DCC. 

To calculate the value of 19, some might consider using 10 (X), 5 (V) and then adding the remaining value. But the remaining value is 4, and symbols cannot be added more than three times. So, here we take: (10 -1 10) = 10 (X) and – 1 10 (- I X), which symbolises XIX.

Hence, the Roman Numeral for 719 will be DCCXIX.

The below table clarifies the basic (1 to 50) conversions of Roman numerals to numbers:

Number Roman Numerals Conversion into decimal numbers
1 I 1
2 II 1 + 1
3 III 1 + 1 + 1
4 IV 5-1
5 V 5
6 VI 5 + 1
7 VII 5 + 1 + 1
8 VIII 5 + 1 + 1 + 1
9 IX 10-1
10 X 10
11 XI 10 + 1
12 XII 10 + 1 + 1
13 XIII 10 + 1 + 1 + 1
14 XIV 10-1 + 5
15 XV 10 + 5
16 XVI 10 + 5 + 1
17 XVII 10 + 5 + 1 + 1
18 XVIII 10 + 5 + 1 + 1 + 1
19 XIX 10-1 + 10
20 XX 10 + 10
21 XXI 10 + 10 + 1
22 XXII 10 + 10 + 1 + 1
23 XXIII 10 + 10 + 1 + 1 + 1
24 XXIV 10 + 10-1 5
25 XXV 10 + 10 + 5
26 XXVI 10 + 10 + 5 + 1
27 XXVII 10 + 10 + 5 + 1 + 1
28 XXVIII 10 + 10 + 5 + 1 + 1 + 1
29 XXIX 10 + 10-1 + 10
30 XXX 10 + 10 + 10
31 XXXI 10 + 10 + 10 + 1
32 XXXII 10 + 10 + 10 + 1 + 1
33 XXXIII 10 + 10 + 10 + 1 + 1 + 1
34 XXXIV 10 + 10 + 10-1 + 5
35 XXXV 10 + 10 + 10 + 5
36 XXXVI 10 + 10 + 10 + 5 + 1
37 XXXVII 10 + 10 + 10 + 5 + 1 + 1
38 XXXVIII 10 + 10 + 10 + 5 + 1 + 1 + 1
39 XXXIX 10 + 10 + 10-1 + 10
40 XL -10 + 50
41 XLI -10 + 50 + 1
42 XLII -10 + 50 + 1 + 1
43 XLIII -10 + 50 + 1 + 1 + 1
44 XLIV -10 + 50-1 + 5
45 XLV -10 + 50 + 5
46 XLVI -10 + 50 + 5 + 1
47 XLVII -10 + 50 + 5 + 1 + 1
48 XLVIII -10 + 50 + 5 + 1 + 1 + 1
49 XLIX -10 + 50-1 + 10
50 L 50

Uses of Roman Numerals

Below are the common examples where Roman numerals are used:

  • The chapters of books are represented by Roman numerals.
  • Many sports events like the Super Bowl, Summer and Winter Olympics use Roman numerals to represent the passage of years. 
  • Many fancy clocks and watches use Roman numerals instead of the Hindu-Arabic numeral systems to give an old-fashioned look.

Conclusion

Roman numerals were discovered as a way to count in ancient Rome. Once the conversion rules are memorised, it becomes quite easy to identify and convert Roman numerals to numbers.