What Is Result Of calc() In CSS
css, css-calc
Solution
The spec does not define very strictly what the computed value of a `calc()` expression is, however it does say that percentages are never calculated as part of the computed value. How exactly this value is represented is left as an implementation detail.
If you see a pixel length instead of a percentage, then that length is the used value, not the computed value, because the pixel value can only be determined after calculating any percentages and laying out elements.
Note that `getComputedStyle()` may return results that are inconsistent with the CSS definition of "computed value". This is one of many unfortunate consequences of browsers doing their own thing back in the 90s.
Problem
We have now started using `calc()` in css, for setting widths on a result of calculation. For example: ``` <div id='parent'> <div id='calcWidth'></div> </div> #parent{ width:100px; } #calcWidth{ width:calc(100% - 3px); height:100px; background:red; } ``` I know how `calc()` works, but I just want to know what is returned in css, in the place of `calc(100% - 3px);` in the example given above. Whats my confusion? In the above example `width:calc(100% - 3px);` say the `100%` width is actually `100px`, which will be determined at runtime by css. So the calculated width will be `100px-3px=97px` 97px and if you convert it to `%` `97%` right? But now, there are two possibilities `97px` is returned, which is set as a width. `97%` is returned, which is set as a width. My Question is: In both cases now the width shall be set to `97px`, but what is returned as a result of `width:calc(100% - 3px);`, `97px` OR `97%` ? you can also see this fiddle: http://jsfiddle.net/8yspnuuw/1/ EDIT: please read See friends: Take a simple example: ``` <div class='parent'> <div class='child'> </div> </div> .parent{ width:200px; } .child{ width:20% } ``` I know the width of child will become 160 px when it is rendered. okay! but thats not what is set in css right? css sets it in %, it is just rendered in pixels. So similarly, using calc, does it return `%` or `pixel` Or to explain my question, read BoltClocks answer, what is the computed value, (and not the used value, i know that is in pixels)