Converting hexadecimal into decimal (denary) is very simple. All we need is to remember that hexadecimal is a base 16 number.  This means that each number column can contain 16 characters.  Hexadecimal goes from 0 to F:

Decimal Number	Hexadecimal Number
0	0
1	1
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	A
11	B
12	C
13	D
14	E
15	F

EG

Using the table – 7 in hex is 7 in decimal.

Using the table – A in hex is 10 in decimal.

---

2 digit Hexadecimal to Denary Conversion

In GCSE computer science you will be expected to convert 2 digit hexadecimal into denary.  Again we need to remember that hexadecimal is a base 16 number and each number column can go from 0-9 and A-F. 

---

Example 1

Convert hexadecimal number A2 into Denary

Put the hexadecimal number into a table with a 16 on the top left and a 1 on the top right. 

16	1
A	2

We need to convert our A into a decimal number.  Anytime there is a letter in either of the columns, we should convert it into its associated number. Using our table, A in hex is 10 in denary. 

16	1
A = 10	2

We now multiply the top column number (the 16 and the 1) by the number on the bottom for each column:

16	1
A = 10	2
16 x 10	1 x 2
= 160	= 2

The final step is to add the 2 columns together

160 + 2 = 162

A2 = 162 in denary. 

---

Example 2

Convert hexadecimal number 28 into Denary

16	1
2	8
16 x 2	1 x 8
= 32	= 8

32 + 8 = 40

28 = 40 in denary