Making input elements the same size as div - html

Question

How do I make the input elements have the same size and alignment as my div elements? (facebookLoginButton and standardLoginButton)
HTML code:
<header>
<div id="topPane">
<h1 id="georgeLogo">G.</h1>
<div id="login">
<div id="facebookLoginButton">Continue with Facebook</div>
<br class="lb">
<div class="center">or</div>
<br class="lb">
<form id="loginForm">
<input type="text" placeholder="Email Address" required>
<br>
<input type="text" placeholder="Password" required>
</form>
<div id="standardLoginButton">Login</div>
</div>
</header>
<div id="bottomPane"></div>
Jsfiddle http://jsfiddle.net/0013v9yj/

Answer 1

In css, apply the same styles to the input... and add display: block to the input
Changed the last css block into this (just added input size on media queries, you only added it in the last of them)
/*********************
MEDIA QUERIES
*********************/
#media only screen and (min-width: 0px) and (max-width: 480px) {
#georgeLogo {
font-size: 6em;
}
#facebookLoginButton, #standardLoginButton, #loginForm input {
font-size: 1.5em;
width: 12.5em;
}
}
#media only screen and (min-width: 481px) and (max-width: 768px) {
#georgeLogo {
font-size: 7em;
}
#facebookLoginButton, #standardLoginButton, #loginForm input {
font-size: 1.5em;
width: 15em;
}
}
#media only screen and (min-width: 769px) {
#georgeLogo {
font-size: 8em;
}
#facebookLoginButton, #standardLoginButton, #loginForm input {
font-size: 2em;
width: 15em;
}
#loginForm {
width: 15em;
}
}

Answer 2

So your issue is that you're using em instead of rem or pixels.
em is relative to its parent, so this can get kind of confusing with the math. If you have an li which is sized at 1.2em and nest another li inside it, it effectively gets a font-size of 1.2 × 1.2 = 1.44em.
rem is not relative to its parent, but to the root of the documnet (default of 16px). However, keep in mind rem is not supported by IE < 9.
In your code, 15 em is a different width for your form and your facebookLoginButton because you keep changing that parent's font-size/em.