function calc_bmi() {
	
	var feet = parseFloat(document.getElementById('bmi_calc_ft').value);
	var inches = parseFloat(document.getElementById('bmi_calc_in').value);
	var weight = parseFloat(document.getElementById('bmi_calc_lbs').value);
	var height = (feet * 12) + inches;

	var bmi = (weight * 703) / (height * height);
	var result = bmi.toFixed(2);
	var resultText;
	
	//do some error checking
	if(!isNumeric(feet) || !isNumeric(inches) || !isNumeric(weight)) {
		resultText = 'Please enter numeric data.';
	} else {
		resultText = 'Your BMI is <span style="font-weight:bold;">' + result + '</span>.';
	}
	document.getElementById('bmi_calc_result').innerHTML = resultText;
	
}

function isNumeric(value){
	var anum=/(^\d+$)|(^\d+\.\d+$)/
	if (anum.test(value))
		return true;
	return false;
}