function calc() {
	var APR = document.getElementById('APR').value;
	var Principal = document.getElementById('Principal').value;
	var Years = document.getElementById('Years').value;
	var DownPmt = document.getElementById('DownPmt').value;
	
	// PMT = principal * (APR / 12) / (1 - (1 + (APR / 12)) ^ term * -12)
	// note the above assumes APR has been divided by 100 already
	// monthly below has been adjusted acccordingly
	
	var monthly = APR / 1200;
	var months = Years * -12;
	
	var onePlus = 1 + monthly;
	var exp = Math.pow(onePlus,months);
	var divisor = 1 - exp;
	var multiple = (Principal - DownPmt) * monthly;
	var result = Math.round(multiple / divisor);
	
	document.getElementById('MonthlyPmt').value = result;
}