Hexadecimal Digit Values

Hexadecimal uses sixteen symbols: the digits 0 to 9 and the letters A to F. The digits keep the values you already know, but the six letters stand in for the denary values ten to fifteen.

A means ten, B means eleven, C means twelve, D means thirteen, E means fourteen and F means fifteen. Letters are used because there are only ten digit symbols and six more are needed, and a letter is easy to tell apart from a digit when you read a value. Each letter is one hexadecimal digit all by itself, yet it is worth a whole number from ten to fifteen, so a D is worth thirteen rather than one. Capitals are usual, but a lower case letter means exactly the same.

Running out of symbols

Because F is the largest single digit, no single symbol can stand for sixteen. Counting on from F works just like counting past 9 in denary: you carry into a new column on the left and start the right-hand column again at 0.

The hexadecimal 10 that follows F is therefore not ten — it is sixteen. The 1 sits in a new column on the left and the 0 shows that no ones are left over. The same carry happens again after 1F, where the next count is written 20.