var units = new Array();
units["tw"] = "cm";
units["tl"] = "cm";
units["rw"] = "me";
units["rl"] = "me";
 
function calctiles() {
	var atw=convrt(document.tiles.tw.value);
	var btw = (units["tw"]=="cm") ? (eval(atw)*0.01) : (eval(atw)*0.0254);
	var atl=convrt(document.tiles.tl.value);
	var btl = (units["tl"]=="cm") ? (eval(atl)*0.01) : (eval(atl)*0.0254);	
	var arw=convrt(document.tiles.rw.value);
	var brw = (units["rw"]=="me") ? (eval(arw)) : (eval(arw)*0.3048);
	var arl=convrt(document.tiles.rl.value);
	var brl = (units["rl"]=="me") ? (eval(arl)) : (eval(arl)*0.3048);	
	var blen=brl/btl;
	var bwid=brw/btw;	
	var blen=blen+"";
	var bwid=bwid+"";	
	var blen=convrt(blen);
	var bwid=convrt(bwid);
	var total=eval(blen)*eval(bwid);
	window.document.tiles.ntr.value=total;	
}
 
function convrt(ip) {
 var poo=ip;
	 var loch=poo.indexOf(".");
	 if (loch==-1) {
		var finl=poo;
	 }else{
		var lg=2;
		var finl=poo.substring(0,loch);
		var finl=eval(finl)+1;
	 }	 
	return finl;
}
 
function csa(){
	units["tw"] = (units["tw"]=="cm") ? "in" : "cm";
}
function csb(){
	units["tl"] = (units["tl"]=="cm") ? "in" : "cm";
}
function csc(){
	units["rw"] = (units["rw"]=="me") ? "fe" : "me";
}
function csd(){
	units["rl"] = (units["rl"]=="me") ? "fe" : "me";
}