Converting Hexadecimal to Decimal

KS3 Computer Science

11-14 Years Old

48 modules covering EVERY Computer Science topic needed for KS3 level.

GCSE Computer Science

14-16 Years Old

45 modules covering EVERY Computer Science topic needed for GCSE level.

A-Level Computer Science

16-18 Years Old

66 modules covering EVERY Computer Science topic needed for A-Level.

GCSE Hexadecimal System (14-16 years)

  • An editable PowerPoint lesson presentation
  • Editable revision handouts
  • A glossary which covers the key terminologies of the module
  • Topic mindmaps for visualising the key concepts
  • Printable flashcards to help students engage active recall and confidence-based repetition
  • A quiz with accompanying answer key to test knowledge and understanding of the module

A-Level Hexadecimal Resources (16-18 years)

  • An editable PowerPoint lesson presentation
  • Editable revision handouts
  • A glossary which covers the key terminologies of the module
  • Topic mindmaps for visualising the key concepts
  • Printable flashcards to help students engage active recall and confidence-based repetition
  • A quiz with accompanying answer key to test knowledge and understanding of the module

Hexadecimal Numbering System

Hexadecimal is a base 16 numbering system which is made up of 16 digits: 0 – 9 and six more, which is A through F.

Uses of Hexadecimal

Hexadecimal numbering system is often used by programmers to simplify the binary numbering system.  Since 16 is equivalent to 24, there is a linear relationship between the numbers 2 and 16.  This means that one hexadecimal digit is equivalent to four binary digits.  Computers use binary numbering system while humans use hexadecimal numbering system to shorten binary and make it easier to understand.

Decimal Numbering System

Decimal is a base 10 numbering system which is made up of 10 numbers: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.  It is the most commonly used numbering system.  The reason behind that is convenience.  We have 10 fingers that we use for counting, so it is easier to count with a base 10 numbering system, thus decimal is widely used.

Conversion from Hexadecimal to Decimal

Conversion can be done by multiplying the hexadecimal number by 16.  Each digit will be multiplied by the corresponding power of 16 value.  It would be easier to convert by putting the hexadecimal on the power of 16 columns as follows:

Exponent162161160
Value256161
Hexadecimal165

Multiply each value by the hexadecimal digit as follows:

(1 x 256) = 256

(6 x 16) = 96

(5 x 1) = 5

Total value = (256 + 96 + 5) = 357

So, the hexadecimal number 165 is 357 in decimal number.

16516 = 35710

Another example, with alphabet hexadecimal digit.

Conversion can be done by multiplying the hexadecimal number by 16.  Each digit will be multiplied by the corresponding power of 16 value.  It would be easier to convert by putting the hexadecimal on the power of 16 columns as follows:

Exponent162161160
Value256161
HexadecimalB28

Multiply each value by the hexadecimal digit as follows:

(B x 256) = (11 x 256) = 2,816

(2 x 16) = 32

(8 x 1) = 8

Total value = (2,816 + 32 + 8) = 2,856

So, the hexadecimal number B28 is 2,856 in decimal number.

B2816 = 2,85610

Conversion from Decimal to Hexadecimal

Conversion can be done by dividing the decimal number by 16 repeatedly until the final result is 0.

For example, the decimal number 357 is converted to hexadecimal number as follows:

DivisionResultRemainder
357 / 16225
22 / 1616
1 / 1601

Hexadecimal number is taken from the remainder starting from the last to the first, or in the illustration above, from bottom to top, which is 165.

Note: For remainder between 0 to 9, hexadecimal equivalent is the same, see table below.

HexadecimalDecimal
00
11
22
33
44
55
66
77
88
99

So decimal number 357 is 165 in hexadecimal number.

35710 = 16516

Another example, with remainder greater than 9, in order to have an alphabet result.

Decimal number 2856 is converted to hexadecimal number as follows:

DivisionResultRemainder
2856 / 161788
178 / 16112
 11 / 16011

Hexadecimal number is taken from the remainder starting from the last to the first, or in the illustration above, from bottom to top, which is 1128.  Looking at the table below, 11 is B in hexadecimal.

HexadecimalDecimal
A10
B11
C12
D13
E14
F15

So decimal number 2856 is B28 in hexadecimal number.

285610 = B2816

Conversion may seem difficult at first, but with just a little practice and understanding the principles behind the conversion, it would be easier over time.  Of course, there are online conversion tools and calculators, but it would be handy to know how it is done manually and understand the concept behind the different numbering systems.