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                <div class="wrapper">
		<div class="inner">
				<div class="content">
						<h1>Ratio padding calculator</h1>
						<p>Enter the width and height of your element to calculate the vertical padding needed to make your element responsive whilst maintaining its aspect ratio.</p>
						<p>Example usage: when using a background image and you need the div to be the height of the image.</p>
						<div class="margin-top">
								<div class="pull-left text-large col-md-6 padding-left-0">
												<input id="width" type="number" maxlength="5" placeholder="Width" class="form-control pull-left">
												<span class="pull-left larger-text">x</span>
												<input id="height" type="number" maxlength="5" placeholder="Height" class="form-control pull-left">
												<input id="btn" type="submit" value="Calculate" class="btn btn-primary">
								<div id="calculation" class="col-md-6 larger-text"></div>


	body {
			height: 100%;
	.wrapper {
			display: table;
			width: 100%;
			height: 100%;
			background: #dee9ff;
	.inner {
			display: table-cell;
			vertical-align: middle;
	.content {
			max-width: 960px;
			margin: auto;
	h1 {
			margin-bottom: 1em;
	p {
			margin-bottom: 1em;
	.margin-top {
			margin-top: 2em;
	.padding-left-0 {
			padding-left: 0;
	input[type=number] {
			width: 150px;
			margin-right: 1em;
	span {
			display: inline-block;
			margin: -0.1em 0.5em 0 0;
	.larger-text {
			font-size: 175%;


                var calcuation = function() {
		"use strict";
		var btn = document.getElementById("btn"),
				w = document.getElementById("width"),
				h = document.getElementById("height"),
				ans = document.getElementById("calculation"),
				output = "";

		btn.addEventListener("click", function(e) {
				output = ((Math.round(h.value) / Math.round(w.value)) * 100).toFixed(2);
				if (output > 0) {
						ans.innerHTML = "padding-top: " + output.replace(".00", "") + "%";
				} else {
						ans.innerHTML = "Invalid dimensions";