FAQ: Sizing Elements - Review: Relative Measurements

This community-built FAQ covers the “Review: Relative Measurements” exercise from the lesson “Sizing Elements”.

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This exercise can be found in the following Codecademy content:

Web Development

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The lesson about relative measurements in CSS says that if I set the width/height of an element as a percentage, I need to set the width/height of its parent element first. However, in the sample website’s code in the same lesson I could not find a single absolute height/width declaration in the CSS of any parent element whose child elements we had to manipulate using percentage values.

Does anyone know why the code still works on the page?

Many thanks

It could be that the parent element was taking the height/width of the browser window itself. Or that the parent element height/width was dictated by the cumulative height/width of the child elements. I’d play around with the code outside of Codecademy (using Visual Studio Code for instance) and see what you can learn through experimentation.

How do we know when to use relative measurements vs hard coded measurements? Does this mean we should stay away from pixels?

Use absolute units (E.g. px) when you want to add fixed dimensions to an element. However, this is not a very common thing to do, so most of the times, you would use relative unit

This review lession states:

When percentages are used to size width and height, child elements will be sized relative to the dimensions of their parent (remember that parent dimensions must first be set).

Why must we set the dimentions of parent elements before using percentages to size child elements? Even if we don’t set the size of parent elements, it would still work, right? Maybe, what this lesson was meant to say is: “to achieve more predictible results, set parent dimentions first”