358

The Less compilers that I'm using (OrangeBits and dotless 1.3.0.5) are aggressively translating

body { width: calc(100% - 250px - 1.5em); }

into

body { width: calc(-151.5%); }

Which is obviously not desired. I'm wondering if there is a way to signal to the Less compiler to essentially ignore the attribute during compilation. I've searched through the Less documentation and both compilers' documentation, and I could not find anything.

Does Less or a Less compiler support this?

If not, is there a CSS extender that does?

TylerH
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Nick Babcock
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    Are you sure you don't want a compiler less agressive? – fiatjaf Aug 15 '13 at 03:43
  • I am very sure too, to want the compiler be more aggressive! (the double negation in the previous comment confused me ;) ) (so my vote as well for the nice feature below) – Andreas Covidiot Jan 08 '15 at 23:53

5 Answers5

557

Less no longer evaluates expression inside calc by default since v3.00.

Original answer (Less v1.x...2.x):

Do this:

body { width: calc(~"100% - 250px - 1.5em"); }

In Less 1.4.0 we will have a strictMaths option which requires all Less calculations to be within brackets, so the calc will work "out-of-the-box". This is an option since it is a major breaking change. Early betas of 1.4.0 had this option on by default. The release version has it off by default.

seven-phases-max
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Luke Page
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    Note that if you're compiling less with twitter's recess it [ignores this escaping](https://github.com/twitter/recess/issues/59). At least at the time of writing this comment. – Attila Fulop Nov 13 '12 at 12:12
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    I just tried `calc(100% - 50px)` in less.css 1.4.0 and the result was `calc(50%)`. The awesome `~"..."` trick continues to work, but I am confused by the "out-of-the-box" statement, which makes me think the above would work. Luke, how does support for `calc` change in Less 1.4.0? Thanks! – Brian M. Hunt Jun 11 '13 at 13:30
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    The question is why did less.js attempt to compute this in the first place? It should throw an error for "100% - 250px" as it can't compute a sensible answer. – mpen Aug 02 '13 at 18:33
  • **Update:** I see there's a `--strict-units` option which prevents these kinds of errors. Awesome! – mpen Aug 02 '13 at 19:28
  • Does this still work? I'm when trying with `calc(~"100% + 20px");` the compiled css is `calc(120%);` note: I am using grunt to build the less and js files – tastybytes Nov 15 '13 at 17:35
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    For future readers, you can also escape just the operator, enabling you to use variables as well. Example: `calc(@somePercent ~"-" @someLength)` – 0b10011 Aug 07 '14 at 20:51
39

A very common usecase of calc is take 100% width and adding some margin around the element.

One can do so with:

@someMarginVariable = 15px;

margin: @someMarginVariable;
width: calc(~"100% - "@someMarginVariable*2);
width: -moz-calc(~"100% - "@someMarginVariable*2);
width: -webkit-calc(~"100% - "@someMarginVariable*2);
Sebastien Lorber
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34

There is several escaping options with same result: 

body { width: ~"calc(100% - 250px - 1.5em)"; }
body { width: calc(~"100% - 250px - 1.5em"); }
body { width: calc(100% ~"-" 250px ~"-" 1.5em); }
icl7126
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11

There's a tidier way to include variables inside the escaped calc, as explained in this post: CSS3 calc() function doesn't work with Less #974

@variable: 2em;

body{ width: calc(~"100% - @{variable} * 2");}

By using the curly brackets you don't need to close and reopen the escaping quotes.

Peter Mortensen
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brohr
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1
@variable: 2em;

body{ 
    width: ~"calc(100% - @{variable} * 2)";
}

Reference: Is there a way to use variables in Less for the ~ operator, like ~"calc(100% - @spacing)";

Sonia Verma
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