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.

Syntax

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

{{CSSSyntax}} 

Description

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

The two operands’ types must be consistent. For lengths, you can’t use 0 to mean 0px (or another length unit). Instead, you must add an explicit unit: margin-top: calc(0px + 20px); is valid, while margin-top: calc(0 + 20px); is invalid. Percentage value types are resolved based on the context. For example, margin-top: calc(50% + 20px); is valid because margin-top resolves percentages to lengths.

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 {{Glossary("whitespace")}} . For instance, calc(50% -8px) will be parsed as “a percentage followed by a negative length” — which is 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”.

Specifications

{{Specifications}} 

See also

• {{CSSxRef("<calc-product>")}} 
• {{CSSxRef("<calc-value>")}} 
• {{CSSxRef("<calc-keyword>")}}