Center a position:fixed element

I would like to make a position: fixed; popup box centered to the screen with a dynamic width and height. I used margin: 5% auto; for this. Without position: fixed; it centers fine horizontally, but not vertically. After adding position: fixed;, it's even not centering horizontally.

Here's the complete set:

.jqbox_innerhtml {
    position: fixed;
    width: 500px;
    height: 200px;
    margin: 5% auto;
    padding: 10px;
    border: 5px solid #ccc;
    background-color: #fff;
}

<div class="jqbox_innerhtml">
    This should be inside a horizontally
    and vertically centered box.
</div>

How do I center this box in screen with CSS?

标签： css css-position centering

12条回答

琉璃瓶的回忆

2楼-- · 2019-01-02 16:54

This solution does not require of you to define a width and height to your popup div.

http://jsfiddle.net/4Ly4B/33/

And instead of calculating the size of the popup, and minus half to the top, javascript is resizeing the popupContainer to fill out the whole screen...

(100% height, does not work when useing display:table-cell; (wich is required to center something vertically))...

Anyway it works :)

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骚的不知所云

3楼-- · 2019-01-02 16:55

To fix the position use this :-

div {
    position: fixed;
    left: 68%;
    transform: translateX(-8%);
}

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其实，你不懂

4楼-- · 2019-01-02 16:56

I want to make a popup box centered to the screen with dynamic width and height.

Here is a modern approach for horizontally centering an element with a dynamic width - it works in all modern browsers; support can be seen here.

Updated Example

.jqbox_innerhtml {
    position: fixed;
    left: 50%;
    transform: translateX(-50%);
}

For both vertical and horizontal centering you could use the following:

Updated Example

.jqbox_innerhtml {
    position: fixed;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
}

You may wish to add in more vendor prefixed properties too (see the examples).

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泛滥B

5楼-- · 2019-01-02 17:00

Add a container like:

div {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  text-align: center;
}

Then put your box into this div will do the work.

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闭嘴吧你

6楼-- · 2019-01-02 17:00

One possible answer:

<!DOCTYPE HTML>
<html>
<head>
    <meta charset="UTF-8">
    <title>CSS Center Background Demo</title>
    <style type="text/css">
        body {
            margin: 0;
            padding: 0;
        }

        div.centred_background_stage_1 {
            position: fixed;
            z-index:(-1 );
            top: 45%;
            left: 50%;
        }

        div.centred_background_stage_2 {
            position: relative;
            left: -50%;

            top: -208px;
            /* % does not work.
               According to the
               http://reeddesign.co.uk/test/points-pixels.html
               6pt is about 8px

               In the case of this demo the background
               text consists of three lines with
               font size 80pt.

               3 lines (with space between the lines)
               times 80pt is about
               ~3*(1.3)*80pt*(8px/6pt)~ 416px

               50% from the 416px = 208px
             */

            text-align: left;
            vertical-align: top;
        }

        #bells_and_wistles_for_the_demo {
            font-family: monospace;
            font-size: 80pt;
            font-weight: bold;
            color: #E0E0E0;
        }

        div.centred_background_foreground {
            z-index: 1;
            position: relative;
        }
    </style>
</head>
<body>
<div class="centred_background_stage_1">
    <div class="centred_background_stage_2">
        <div id="bells_and_wistles_for_the_demo">
            World<br/>
            Wide<br/>
            Web
        </div>
    </div>
</div>
<div class="centred_background_foreground">
    This is a demo for <br/>
    <a href="http://stackoverflow.com/questions/2005954/center-element-with-positionfixed">
        http://stackoverflow.com/questions/2005954/center-element-with-positionfixed
    </a>
    <br/><br/>
    <a href="http://www.starwreck.com/" style="border: 0px;">
        <img src="./star_wreck_in_the_perkinnintg.jpg"
             style="opacity:0.1;"/>
    </a>
    <br/>
</div>
</body>
</html>

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还给你的自由

7楼-- · 2019-01-02 17:03

Just add:

left: calc(-50vw + 50%);
right: calc(-50vw + 50%);
margin-left: auto;
margin-right: auto;

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