Check out example codes for "css calc". It will help you in understanding the concepts better.

Code Example 1

```
div {
width: calc(100% - 100px);
}
```

Code Example 2

```
body {
width: calc(100vw - 8px);
height: calc(100vh - 8px);
}
```

Code Example 3

```
/* Answer to: "css calc height" */
/*
Assuming you're not sure what the calc() function does:
calc() is a native CSS way to do simple math right in CSS as a
replacement for any length value (or pretty much any number
value). It has four simple math operators: add (+), subtract (-),
multiply (*), and divide (/). Being able to do math in code is
nice and a welcome addition to a language that is fairly number
heavy.
For a couple of use cases and examples for calc() go to:
https://css-tricks.com/a-couple-of-use-cases-for-calc/
Here's a list of all the cases:
Case 1: (All The Height – Header)
Case 2: X Pixels From Bottom Right Corner
Case 3: Fixed Gutters Without Parents
Case 4: Showing Math Is Easier To Understand
Case 5. Kinda Crappy box-sizing Replacement
*/
```

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