The <calc-sum> CSS data type represents an expression which performs a calculation in any CSS math function. The expression executes a basic arithmetic operation of addition and subtraction between two values.


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.

Formal syntax

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

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

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

<calc-keyword> =
e |
pi |
infinity |
-infinity |

<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.


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Browser compatibility

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See also