Rules for Writing Roman Numerals

Rules for Writing Roman Numerals

Roman Numerals

Try the Roman Numeral Challenge.

Roman numerals are expressed by letters of the alphabet:

I=1

V=5

X=10

L=50

C=100

D=500

M=1000

There are four basic principles for reading and writing Roman numerals:

• 1. A letter repeats its value that many times (XXX = 30, CC = 200, etc.). A letter can only be repeated three times.
• 2. If one or more letters are placed after another letter of greater value, add that amount.

VI = 6 (5 + 1 = 6)

LXX = 70 (50 + 10 + 10 = 70)

MCC = 1200 (1000 + 100 + 100 = 1200)

3. If a letter is placed before another letter of greater value, subtract that amount.

IV = 4 (5 – 1 = 4)

XC = 90 (100 – 10 = 90)

CM = 900 (1000 – 100 = 900)

Several rules apply for subtracting amounts from Roman numerals:

• a. Only subtract powers of ten (I, X, or C, but not V or L)

For 95, do NOT write VC (100 – 5). 
DO write XCV (XC + V or 90 + 5)

• b. Only subtract one number from another.

For 13, do NOT write IIXV (15 – 1 - 1). 
DO write XIII (X + I + I + I or 10 + 3)

• c. Do not subtract a number from one that is more than 10 times greater (that is, you can subtract 1 from 10 [IX] but not 1 from 20—there is no such number as IXX.)

For 99, do NOT write IC (C – I or 100 - 1). 
DO write XCIX (XC + IX or 90 + 9)

• 4. A bar placed on top of a letter or string of letters increases the numeral's value by 1,000 times.

XV = 15,  = 15,000

One	I	Eleven	XI	Thirty	XXX
Two	II	Twelve	XII	Forty	XL
Three	III	Thirteen	XIII	Fifty	L
Four	IV	Fourteen	XIV	Sixty	LX
Five	V	Fifteen	XV	Seventy	LXX
Six	VI	Sixteen	XVI	Eighty	LXXX
Seven	VII	Seventeen	XVII	Ninety	XC
Eight	VIII	Eighteen	XVIII	One hundred	C
Nine	IX	Nineteen	XIX	Five hundred	D
Ten	X	Twenty	XX	One thousand	M

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Roman Numerals 1-100
1= I  2 = II  3 = III  4 = IV  5 = V  6 = VI  7 = VII  8 = VIII  9 = IX  10 = X  11 = XI  12 = XII  13 = XIII  14 = XIV  15 = XV  16 = XVI  17 = XVII  18 = XVIII  19 = XIX  20 = XX  21 = XXI  22 = XXII  23 = XXIII  24 = XXIV  25 = XXV	26 = XXVI  27 = XXVII  28 = XXVIII  29 = XXIX  30 = XXX  31 = XXXI  32 = XXXII  33 = XXXIII  34 = XXXIV  35 = XXXV  36 = XXXVI  37 = XXXVII  38 = XXXVIII  39 = XXXIX  40 = XL  41 = XLI  42 = XLII  43 = XLIII  44 = XLIV  45 = XLV  46 = XLVI  47 = XLVII  48 = XLVIII  49 = XLIX  50 = L	51 = LI  52 = LII  53 = LIII  54 = LIV  55 = LV  56 = LVI  57 = LVII  58 = LVIII  59 = LIX  60 = LX  61 = LXI  62 = LXII  63 = LXIII  64 = LXIV  65 = LXV  66 = LXVI  67 = LXVII  68 = LXVIII  69 = LXIX  70 = LXX  71 = LXXI  72 = LXXII  73 = LXXIII  74 = LXXIV  75 = LXXV	76 = LXXVI  77 = LXXVII  78 = LXXVIII  79 = LXXIX  80 = LXXX  81 = LXXXI  82 = LXXXII  83 = LXXXIII  84 = LXXXIV  85 = LXXXV  86 = LXXXVI  87 = LXXXVII  88 = LXXXVIII  89 = LXXXIX  90 = XC  91 = XCI  92 = XCII  93 = XCIII  94 = XCIV  95 = XCV  96 = XCVI  97 = XCVII  98 = XCVIII  99 = XCIX  100 = C