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There are many ways you can use calc() in your projects. This video covers simple examples that demonstrate the basics of calc().
Resources
calc() operators

+
Addition 

Subtraction 
*
Multiplication 
/
Division

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[SOUND] Hey everyone!

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Guil here, one of the front end teachers here at Treehouse.

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Did you know that you can do simple math operations with CSS?

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In this workshop series, I'm going to teach you how to use

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the CSS calc function, to add a little logic to your CSS.

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First, you'll learn the basics of calc.

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Then I'm going to cover 3 useful ways you can use calc in your web projects.

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Like setting background position offsets, displaying full width elements

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inside padded containers, and creating fluid grid columns.

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calc is a CSS function that performs a calculation and returns a result.

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With calc, you use operators like the plus sign, minus sign, asterisk and

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forward slash to write mathematical expressions that add,

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subtract, multiply and divide values.

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[NOISE] You use the calc function and property values wherever CSS, length, and

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number values are accepted.

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There are many ways you can use calc in your projects.

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So let's start with something really simple to demonstrate

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how the calc function works.

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And later on in the workshop, I'll show you a few handy use cases for calc.

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To follow along in work spaces, click the launch workspace button on this page.

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In the workspace, there's a simple webpage link to a style sheet.

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This index.html file contains a div element with the class,

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"column," and when I preview this page in the browser

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we can see that the column element takes up the full width and height of the page.

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So first, I'll show you how to define width and height values using calc.

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Back in my workspace I'm going to open up the style.css file ,and scroll down

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to the column rule.

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In the column rule I'm going to replace the width value

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of 100% with the value calc.

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So I'm going to type calc, followed by a set of parenthesis.

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Inside the parenthesis is where we write mathematical expressions that add,

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subtract, multiply and divide values.

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And the result of the expression is used as the properties value.

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So I'll start with a simple expression to demonstrate how they work.

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So inside the parentheses using a subtraction operator,

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I'm going to write the expression (150px 50px).

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An expression is evaluated from the left to the right.

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So when the browser calculates 150 pixels minus 50 pixels.

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The result is a 100 pixel wide column element.

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Now if I go back and use the addition operator to change the expression to

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(150px + 50px), the result is now a 200 pixel wide column.

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Knowing that CSS can do math is pretty exciting and impressive.

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But in these examples, you're better off using 100 pixels or

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200 pixels as the width value.

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There's no added benefit in using calc for simple pixel based expressions like this.

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What's most useful about using calc, is how you're able to mix units like

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percentages and pixels, or ems and rems in your expressions.

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This gives you greater control over your layouts.

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For instance, say I'm working with a fluid layout,

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where I don't know the exact width of the parent container.

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And in the container, I want to define a column width that's exactly

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50 pixels less than half of the parent container's width.

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Well I can calculate the width within the CSS,

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using the expression (50% 50px).

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In the expression I'm defining the value 50% for

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half the parent container's width, then subtracting 50 pixels.

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So when we take a look at it in the browser we see how the column will

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always be 50 pixels narrower than half the view port width.

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Even though I use a fixed pixel value in the expression,

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I'm still able to define a fluid width in my layout.

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This is what I meant earlier when I said being able to mix units,

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gives you greater control over a layout.

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Now, if I want a column that's slighter wider then 50%,

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I can use an addition operator.

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So I'm going to change the expression to (50% + 2em).

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So here one em is equal to 16 pixels, so

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now the column container is 32 pixels wider than half the view port size.

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I can also use the calc expression to define the height.

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So I'll go back to my column rule and change the height value to calc and

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then inside the parenthesis I'm going to write the expression 100% minus 3em.

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So when I save my file and refresh the browser,

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you can see how the columns height will always be three em, or

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48 pixels, shorter than the full height of it's container.

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In this case, it's the view port.

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When using addition and subtraction operators in expressions,

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there needs to be a space on both sides of the operators,

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otherwise the browser cannot calculate them.

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For example, if I remove the space between the minus operator and the value 3em,

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the expression 100% negative 3em is now considered invalid, because the browser

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interprets this as a percentage value followed by a negative end value.

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So it cannot calculate this.

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So be sure to use white space around the minus and plus operators.

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So that they're not interpreted as positive or negative values.

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So now that you've learned the basics of calc, in the lessons that follow this

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video you're going to learn three useful ways you can use calc in your projects.
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