垂直居中

flex (子级宽高未知)

父级增加属性 display: flex; 、justify-content: center; 、align-items: center;

1
2
3
4
5
6
7
8
9
10
11
12
13
<style>
    .box {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        display: flex;      
        justify-content: center;
        align-items: center;
    }
</style>
<div class="box">
    <div class="item">1</div>
</div>

定位 + CSS3 (子级宽高未知)

父级 position: relative; ,子级 position: absolute; 、top: 50%; 、left: 50%;、transform: translate(-50%,-50%);

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
<style>
    .box {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        position: relative;
    }
    .item{
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%,-50%);
    }
</style>
<div class="box">
    <div class="item">1</div>
</div>

定位 (子级宽高未知)

父级 position: relative; ,子级 position: absolute; 、top: 0; 、bottom: 0; 、left: 0; 、right: 0; 、margin: auto;

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
<style>
    .box {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        position: relative;
    }
   .item{
        width: 50px;
        height: 50px;
        background: red;
        position: absolute;
        top: 0;
        bottom: 0;
        left: 0;
        right: 0;
        margin: auto;
    }
</style>
<div class="box">
    <div class="item">1</div>
</div>

定位 (子级宽高已知)

父级 position: relative; ,子级 position: absolute; 、top: 50%; 、left: 50%;、margin-top: -高一半 、margin-left: -宽一半

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
<style>
    .box {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        position: relative;
    }
    .item{
        position: absolute;
        width: 50px;
        height: 50px;
        top: 50%;
        left: 50%;
        margin-left: -25px;
        margin-top: -25px;
    }
</style>
<div class="box">
    <div class="item">1</div>
</div>

table-cell (子级宽高未知)

父级 display: table-cell; 、text-align: center; 、vertical-align: middle; ，子级 display: inline-block;

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
<style>
    .box {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        display: table-cell;
        text-align: center;
        vertical-align: middle;
    }
    .item{
        width: 50px;
        height: 50px;
        background: red;
        display: inline-block;
    }
</style>
<div class="box">
    <div class="item">1</div>
</div>

或者

父级 display: table-cell; 、vertical-align: middle; ，子级 display: block;、margin: 0 auto;

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
<style>
    .box {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        display: table-cell;
        vertical-align: middle;
    }
    .item{
        width: 50px;
        height: 50px;
        background: red;
        display: block;
        margin: 0 auto;
    }
</style>
<div class="box">
    <div class="item">1</div>
</div>