I am trying to create a body fat calculator but I am not sure if my equations are correct. I feel like im missing a variable? I am not too sure about my equation for javascript. Please explain why you did what you did.

Code:

<html>
<head>
<title> BodyFat Formula </title>
<script type="text/javascript">
function BodyFat(weight, waist){
var weight, waist, bodyfat, total bodyfat
if ((weight >=0) , (waist >=0) , (total bodyfat >=0))
weight = Math.round(weightBox x 1.082) + 94.42
waist = Math.round(waistBox x 4.15)
bodyfat = (weight - waist)
total bodyfat = Math.round(bodyfat x 100) / total bodyfat)
weight = parseInt(document.getElementById("weightBox").value;
waist = parseInt(document.getElementById("waistBox").value;
bodyfat = = parseInt(document.getElementById("bodyfatBox").value;
// Assumes: weightBox contains the person's weight in pounds
// Assumes: waistBox contains the person's waist measurement in inches
// converts the weight and the waist measurement into numeric values
// calculates the BodyFat using the following Body Fat Formula(For Men):
// Factor1: (Total body weight x 1.082) + 94.42
// Factor2: Waist measurement x 4.15
// Lean Body Mass: Factor1 - Factor2
// Body Fat Weight: Total body weight - Lean Body Mass
// Body Fat Percentage: Rounded( (Body Fat Weight x 100) / total bodyweight )
}
</script>
</head>
<body>
<h2>BodyFat Formula</h2>
<p>
Weight: <input type="text" id="weightBox" size=4 value=150> pounds <br>
Waist measurement: <input type="text" id="waistBox" size=4 value=32> inches<br>
BodyFat: <input type="text" id="bodyfatBox" size=4 value=0> percent
</p>
<input type="button" value="Calculate body fat" onclick="BodyFat();">
<hr>
<div id="outputDiv"></div>
</body>
</html>