CSS Input with width: 100% goes outside parent'

Question

I am trying to make a login form constituted of two input fields with an inset padding, but those two fields always end up exceeding its parent's boundaries; the issue stems from the added inset padding. What could be done in order to rectify this issue?

JSFiddle snippet: http://jsfiddle.net/4x2KP/

N.B.: The code may not be at its cleanest. For instance, the span element that encapsulates the text inputs may not be needed at all.

    #mainContainer {
    	line-height: 20px;
    	font-family: "Helvetica Neue",Helvetica,Arial,sans-serif;
        background-color: rgba(0,50,94,0.2);
    	margin: 20px auto;
    	display: table;
    	-moz-border-radius: 15px;
    	border-style: solid;
    	border-color: rgb(40, 40, 40);
    	border-radius: 2px 5px 2px 5px / 5px 2px 5px 2px;
    	border-radius: 2px;
    	border-radius: 2px 5px / 5px;
    	box-shadow: 0 5px 10px 5px rgba(0,0,0,0.2);
    }
    
    .loginForm {
    	width: 320px;
    	height: 250px;
    	padding: 10px 15px 25px 15px;
    	overflow: hidden;
    }
    
    .login-fields > .login-bottom input#login-button_normal {
    	float: right;
    	padding: 2px 25px;
    	cursor: pointer;
    	margin-left: 10px;
    }
    
    .login-fields > .login-bottom input#login-remember {
    	float: left;
    	margin-right: 3px;
    }
    
    .spacer {
    	padding-bottom: 10px;
    }
    
    /* ELEMENT OF INTEREST HERE! */
    input[type=text],
    input[type=password] {
        width: 100%;
    	height: 20px;
    	padding: 5px 10px;
    	background-color: rgb(215, 215, 215);
        line-height: 20px;
        font-size: 12px;
        color: rgb(136, 136, 136);
        border-radius: 2px 2px 2px 2px;
        border: 1px solid rgb(114, 114, 114);
    	box-shadow: 0 1px 0 rgba(24, 24, 24,0.1);
    }
    
    input[type=text]:hover,
    input[type=password]:hover,
    label:hover ~ input[type=text],
    label:hover ~ input[type=password] {
     	background:rgb(242, 242, 242) !important;
    }
    
    input[type=submit]:hover {
      box-shadow:
        inset 0 1px 0 rgba(255,255,255,0.3),
        inset 0 -10px 10px rgba(255,255,255,0.1);
    }

    <div id="mainContainer">
        <div id="login" class="loginForm">
            <div class="login-top">
            </div>
            <form class="login-fields" onsubmit="alert('test'); return false;">
                <div id="login-email" class="login-field">
                    <label for="email" style="-moz-user-select: none;-webkit-user-select: none;" onselectstart="return false;">E-mail address</label>
                    <span><input name="email" id="email" type="text"></input></span>
                </div>
                <div class="spacer"></div>
                <div id="login-password" class="login-field">
                    <label for="password" style="-moz-user-select: none;-webkit-user-select: none;" onselectstart="return false;">Password</label>
                    <span><input name="password" id="password" type="password"></input></span>
                </div>
                <div class="login-bottom">
                    <input type="checkbox" name="remember" id="login-remember"></input>
                    <label for="login-remember" style="-moz-user-select: none;-webkit-user-select: none;" onselectstart="return false;">Remember my email</label>
                    <input type="submit" name="login-button" id="login-button_normal" style="cursor: pointer" value="Log in"></input>
                </div>
            </form>
        </div>
    </div>

Answer 1

Padding is added to the overall width. Because your container has a pixel width, you are better off giving the inputs a pixel width too, but remember to remove the padding and border from the width you set to avoid the same issue.

Answer 2

I tried these solutions but never got a conclusive result. In the end I used proper semantic markup with a fieldset. It saved having to add any width calculations and any box-sizing.

It also allows you to set the form width as you require and the inputs remain within the padding you need for your edges.

In this example I have put a border on the form and fieldset and an opaque background on the legend and fieldset so you can see how they overlap and sit with each other.

<html>
  <head>
  <style>
    form {
      width: 300px;
      margin: 0 auto;
      border: 1px solid;
    }
    fieldset {
      border: 0;
      margin: 0;
      padding: 0 20px 10px;
      border: 1px solid blue;
      background: rgba(0,0,0,.2);
    }
    legend {
      background: rgba(0,0,0,.2);
      width: 100%;
      margin: 0 -20px;
      padding: 2px 20px;
      color: $col1;
      border: 0;
    }
    input[type="email"],
    input[type="password"],
    button {
      width: 100%;
      margin: 0 0 10px;
      padding: 0 10px;
    }
    input[type="email"],
    input[type="password"] {
      line-height: 22px;
      font-size: 16px;
    }
    button {
    line-height: 26px;
    font-size: 20px;
    }
  </style>
  </head>
  <body>
  <form>
      <fieldset>
          <legend>Log in</legend>
          <p>You may need some content here, a message?</p>
          <input type="email" id="email" name="email" placeholder="Email" value=""/>
          <input type="password" id="password" name="password" placeholder="password" value=""/>
          <button type="submit">Login</button>
      </fieldset>
  </form>
  </body>
</html>

Answer 3

Do you want the input fields to be centered? A trick to center elements: specify the width of the element and set the margin to auto, eg:

margin : 0px auto;
width:300px

A link to your updated fiddle:

http://jsfiddle.net/4x2KP/5/