rem()
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The rem()
CSS function returns a remainder left over when the first parameter is divided by the second parameter, similar to the JavaScript 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.
For example, the CSS
rem(27, 5)
function returns the remainder of2
. When dividing 27 by 5, the result is 5 with a remainder of 2. The full calculation is27 / 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 */
Parameter
The rem(dividend, divisor)
function accepts two comma-separated values as its parameters. Both parameters must have the same type, number, dimension, or percentage, for the function to be valid. While the units in the two parameters don't need to be the same, they do need of the same dimension type, such as <length>
, <angle>
, <time>
, or <frequency>
to be valid.
dividend
-
A calculation that resolves to a
<number>
,<dimension>
, or<percentage>
representing the dividend. divisor
-
A calculation that resolves to a
<number>
,<dimension>
, or<percentage>
representing the divisor.
Return value
Returns a <number>
, <dimension>
, or <percentage>
(corresponds to the parameters' type) representing the remainder, that is, the operation left over.
- If
divisor
is0
, the result isNaN
. - If
dividend
isinfinite
, the result isNaN
. - If
dividend
is positive the result is positive (0⁺
), and ifdividend
is negative the result is negative (0⁻
).
Formal syntax
<rem()> =
rem( <calc-sum> , <calc-sum> )
<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
Specifications
Specification |
---|
CSS Values and Units Module Level 4 # funcdef-rem |
Browser compatibility
BCD tables only load in the browser