rem()

Baseline 2024
Newly available

Since ⁨May 2024⁩, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The rem() remainder operator (%). The remainder is the value left over when one operand, the dividend, is divided by a second operand, the divisor. It always takes the sign of the dividend.

Note: To read about the unit rem, see the <length> page.

For example, the CSS rem(27, 5) function returns the remainder of 2. When dividing 27 by 5, the result is 5 with a remainder of 2. The full calculation is 27 / 5 = 5 * 5 + 2.

Syntax

css
/* Unitless <number> */
line-height: rem(21, 2); /* 1 */
line-height: rem(14, 5); /* 4 */
line-height: rem(5.5, 2); /* 1.5 */

/* Unit based <percentage> and <dimension> */
margin: rem(14%, 3%); /* 2% */
margin: rem(18px, 5px); /* 3px */
margin: rem(10rem, 6rem); /* 4rem */
margin: rem(26vmin, 7vmin); /* 5vmin */
margin: rem(1000px, 29rem); /* 72px - if root font-size is 16px */

/* Negative/positive values */
rotate: rem(200deg, 30deg); /* 20deg */
rotate: rem(140deg, -90deg); /* 50deg */
rotate: rem(-90deg, 20deg); /* -10deg */
rotate: rem(-55deg, -15deg); /* -10deg */

/* Calculations */
scale: rem(10 * 2, 1.7); /* 1.3 */
rotate: rem(10turn, 18turn / 3); /* 4turn */
transition-duration: rem(20s / 2, 3000ms * 2); /* 4s */

Parameters

The rem(dividend, divisor) function accepts two comma-separated values as its parameters. Both parameters must have the same type, <length>, <frequency> to be valid.

dividend

A calculation that resolves to a <percentage> representing the dividend.

divisor

A calculation that resolves to a <percentage> representing the divisor.

Return value

Returns a <percentage> (corresponds to the parameters' type) representing the remainder, that is, the operation left over.

  • If divisor is 0, the result is NaN.
  • If dividend is infinite, the result is NaN.
  • If dividend is positive the result is positive (0⁺), and if dividend is negative the result is negative (0⁻).

Formal syntax

<rem()> = 
rem( <calc-sum> , <calc-sum> )

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

<calc-value> =
|
|
pi |
NaN

Specifications

Specification
CSS Values and Units Module Level 4
# funcdef-rem

Browser compatibility

See also

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