This is name given to numbers using the base-16 notation.

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

The decimal numbers 10 to 15 are represented with the letters A to F. There are 16 values, hence why it is a base-16 number system.

Hexadecimal is widely used in computing because it is a much shorter way of representing a byte of data. If we were to represent a byte of data in binary, it would require 8 digits, e.g. 11111111.

However, that same byte of data could be represented in hexadecimal in just two digits e.g. FF - much more compact and user friendly than a binary number.

The table above only shows hexadecimal numbers up to denary 15. The largest byte value is 255 and you can use hexadecimal numbers to represent up to this value.

We can extend the table above to show the next set of hexadecimal numbers:

 Decimal 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Hexadecimal 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F

Once we have gone past the first 16 numbers, a 1 is added in front of the next 16 numbers (similar to denary when we go from 0-9 and then the next 10 numbers have a 1 in front of them)

The next set of hexadecimal numbers would have a 2 in front of them:

 Decimal 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Hexadecimal 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F

See if you can complete the table for the next set:

 Decimal 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Hexadecimal

Hex Decimal Calculator
0F 15 decimal
10 16 decimal (1x16)
20 32 decimal (2x16)
30 48 decimal (3x16)
40 64 decimal (4x16)
50 80 decimal (5x16)
60 96 decimal (6x16)
70 112 decimal (7x16)
80 128 decimal (8x16)
90 144 decimal (9x16)
A0 160 decimal (10x16)

As you can see, the second digit in a hex number is multiplied by 16 to work out the decimal equivalent so the 4 x 16 = 64

Challenge see if you can find out one extra fact on this topic that we haven't already told you