在做移动端前端开发的时候，常常遇到这样的问题，需要用rem来实现设备的自适应。但苦于rem和px的转换却又忘而却步。

1.首先要确认UI的设计稿的基准是按照哪种设备宽度的机型设计的，通常的设计稿是按照iphone6 plus也就是宽度750px来设计的。这样我们拿到手之后就要把如下的responsive.css中的 @media screen and (min-width: 320px) 设置成为font-size: 100px;

2.引入responsive.css成功后，之后在写页面样式的时候就可以按照 设计稿上显示宽度 除以 2 除以 100 得到。例如：100px/2/100 = 0.5rem;

/***** responsive font lastmodify zhancheng 由于UE目前都按375为1:2比例计算，所以默认370px为font-size:100px!important; *****/ @media screen and (min-width: 320px) { html { /*font-size: 100px!important;*/ font-size: 84.375px!important; } } @media screen and (min-width: 330px) { html { /*font-size: 103.125px!important;*/ font-size: 87.5px!important; } } @media screen and (min-width: 340px) { html { /*font-size: 106.25px!important;*/ font-size: 90.625px!important; } } @media screen and (min-width: 350px) { html { /*font-size: 109.375px!important;*/ font-size: 93.75px!important; } } @media screen and (min-width: 360px) { html { font-size: 96.875px!important; /*font-size: 112.5px!important;*/ } } @media screen and (min-width: 370px) { html { /*font-size: 115.625px!important;*/ font-size: 100px!important; } } @media screen and (min-width: 380px) { html { /*font-size: 118.75px!important;*/ font-size: 103.125px!important; } } @media screen and (min-width: 390px) { html { /*font-size: 121.875px!important;*/ font-size: 106.25px!important; } } @media screen and (min-width: 400px) { html { /*font-size: 125px!important;*/ font-size: 109.375px!important; } } @media screen and (min-width: 410px) { html { /*font-size: 128.125px!important;*/ font-size: 112.5px!important; } } @media screen and (min-width: 420px) { html { /*font-size: 131.25px!important;*/ font-size: 115.625px!important; } } @media screen and (min-width: 430px) { html { /*font-size: 134.375px!important;*/ font-size: 117.75px!important; } } @media screen and (min-width: 440px) { html { /*font-size: 137.5px!important;*/ font-size: 120.875px!important; } } @media screen and (min-width: 450px) { html { /*font-size: 140.625px!important;*/ font-size: 124px!important; } } @media screen and (min-width: 460px) { html { /*font-size: 143.75px!important;*/ font-size: 127.125px!important; } } @media screen and (min-width: 470px) { html { /*font-size: 146.875px!important;*/ font-size: 130.25px!important; } } @media screen and (min-width: 480px) { html { /*font-size: 150px!important;*/ font-size: 133.375px!important; } } @media screen and (min-width: 490px) { html { /*font-size: 153.125px!important;*/ font-size: 136.5px!important; } } @media screen and (min-width: 500px) { html { /*font-size: 156.25px!important;*/ font-size: 139.625px!important; } } @media screen and (min-width: 639px) { html { /*font-size: 200px!important;*/ font-size: 142.75px!important; } } @media screen and (min-width: 719px) { html { /*font-size: 225px!important;*/ font-size: 135.875px!important; } } @media screen and (max-width: 319px) { html { font-size: 84.375px!important; } }