JSFiddle - React, Tailwind, and code Playground

HTML

<div>
<h1>Startup Metrics Calculator</h1>
<h2 id="1"></h1>
<p id="2"></p>
<h3 id="3"></h2>
<p id="4"></p>
<h3 id="5"></h2>
<p id="6"></p>
<h3 id="7"></h2>
</div>
<h1 class="put"> <== Put your values in over here.</h1>

CSS

@import url(http://fonts.googleapis.com/css?family=Open+Sans+Condensed:300,300italic,700);
body {
    background-color:#E9E9E9;
    color: #353535;
    font-family: 'Open Sans Condensed', sans-serif;
    font-size:1.2em;
}

h3 {
    padding-left:20px;
}

div {
    padding-left:10%;
    padding-right:10%;
    width:80%;
     text-align:center;
}

.put {
    padding-top:50px;
}

JavaScript

// Membership Cost
var membership = 10;
// Starting number of customers
var customers = 10;
// Months projected
var time = 48;
// Percent of customer growth per month
var growth = 10;
// Cost per member per month
var costmember = 1;
// Starting money
var net = 0;

for (month=0;month<time;month++) {
     customers+= customers*(growth/100);
     net += membership*customers;
     net -= membership*costmember;
}

$("#1").text(time + " month projection.");
$("#2").text("Ammount of customers obtained after " + time + " months with a customer acquisition rate of " + growth + "% increase per month.");
$("#3").text(Math.round(customers) + " customers");
$("#4").text("Ammount of money obtained after " + time + " months with membership being $" + membership + " per month, and cost per customer being $" + costmember + ".");
$("#5").text("$"+Math.round(net));
$("#6").text("Income per month at month " + time + ".");
$("#7").text("$"+Math.round(((membership-costmember)*customers)));