The <calc-sum> type defines two numeric values and one of the following arithmetic operators between them.

+

Adds two numbers together.

-

Subtracts the right number from the left.

<calc-sum> = 
  <calc-product> [ [ '+' | '-' ] <calc-product> ]*  

<calc-product> = 
  <calc-value> [ [ '*' | '/' ] <calc-value> ]*  

<calc-value> = 
  <number>         |
  <dimension>      |
  <percentage>     |
  <calc-constant>  |
  ( <calc-sum> )   

<calc-constant> = 
  e          |
  pi         |
  infinity   |
  -infinity  |
  NaN        

<calc-sum> = 
  <calc-product> [ [ '+' | '-' ] <calc-product> ]*  

The operands in the expression may be any <length> syntax value. You can use <length>, <frequency>, <angle>, <time>, <percentage>, <number>, or <integer>.

Different unit types can be used in a single expression. For example, subtracting px from %, as in calc(100% - 10px), is a valid expression.

Including CSS variables in calc-sum expressions is also allowed. The following code calc(10px + var(--variable)), is a valid expression.

The + and - operators must be surrounded by whitespace. For instance, calc(50% -8px) will be parsed as a percentage followed by a negative length — an invalid expression — while calc(50% - 8px) is a percentage followed by a subtraction operator and a length. Likewise, calc(8px + -50%) is treated as a length followed by an addition operator and a negative percentage.

• <calc-product>
• <calc-value>
• <calc-constant>