CSS width subtraction

Question

How to subtract width in CSS?

For example:

width = 100% - 10px 

I'm not talking about padding or margin.

Answer 1

Now with calc the solution will be :

width: calc(100% - 10px); 

Calc can be use with Addition, Subtraction, Multiplication, Division.

Additional note :

Note: The + and - operators must always be surrounded by whitespace. The operand of calc(50% -8px) for instance will be parsed as a percentage followed by a negative length, an invalid expression, while the operand of calc(50% - 8px) is a percentage followed by a minus sign and a length. Even further, calc(8px + -50%) is treated as a length followed by a plus sign and a negative percentage. The * and / operators do not require whitespace, but adding it for consistency is allowed, and recommended.

Answer 2

Simple: you can't do this. You'll have to use some workaround.