function calcPaint()
{
	//validate fields
	var areaValue = parseInt(document.getElementById('area').value);
	
	if (isNaN(areaValue)) {alert('Please enter an integer for area'); return;}
	
	var surfaceTypeAdj;
	
	switch(document.getElementById('type').value)
	{
		case "Plaster":
			surfaceTypeAdj = 1.05;
			break;
		case "Rhinolite":
			surfaceTypeAdj = 1.0;
			break;
		case "Gypsum":
			surfaceTypeAdj = 1.0;
			break;
		case "Pressed":
			surfaceTypeAdj = 1.0;
			break;
		case "Prefabricated":
			surfaceTypeAdj = 1.05;
			break;
		case "Wood":
			surfaceTypeAdj = 1.1;
			break;
		case "Exposed":
			surfaceTypeAdj = 1.1;
			break;
		case "Presmooth":
			surfaceTypeAdj = 1.1;
			break;
		case "Precon" :
			surfaceTypeAdj = 1.5;
			break;
	}
	
	var paintedAdj;
	
	switch(document.getElementById('painted').value)
	{
		case "yes":
			paintedAdj = 1.0;
			break;
		case "no":
			paintedAdj = 1.15;
			break;
	}
	
	var spreadRate;
	var coatsReq = 1;
	
	switch(document.getElementById('paints').value)
	{
		case "Silk":
			spreadRate = 7;
			coatsReq = 2;
			break;
		case "Matt": 
			spreadRate = 5;
			coatsReq = 2;
			break;
		case "Bond": 
			spreadRate = 8;
			break;
		case "Plaster":
			spreadRate = 5;
			break;
		case "Polyglo":
			spreadRate = 8;
			coatsReq = 2;
			break;
		case "GP":
			spreadRate = 4;
			coatsReq = 2;
			break;
		case "Coverkote":
			spreadRate = 4;
			coatsReq = 2;
			break;
		case "Wood":
			spreadRate = 8;
			break;
		case "Universal":
			spreadRate = 5;
			break;
	}
	
	var profileAdj;
	
	switch(document.getElementById('profile').value)
	{
		case "Smooth":
			profileAdj = 1.0;
			break;
		case "Slightly":
			profileAdj = 1.1;
			break;
		case "Coarse":
			profileAdj = 1.2;
			break;
		case "Scratch Plaster":
			profileAdj = 1.3;
			break;
	}
	
	var coat1 = 0;
	var coat2 = 0;
	
	switch(coatsReq)
	{
		case 1:
			coat1 = (areaValue / (spreadRate)) * profileAdj * paintedAdj * surfaceTypeAdj;
			break;
		case 2:
			coat1 = (areaValue / (spreadRate)) * profileAdj * paintedAdj * surfaceTypeAdj;
			coat2 = (areaValue / (spreadRate)) * profileAdj * paintedAdj * surfaceTypeAdj;
    		break;
	}
	
	var totPaint = Math.ceil(coat1 + coat2);
	document.getElementById('paintreq').value = totPaint;
	document.getElementById('coats').value = coatsReq;
}