function calculate() {
          var m;
          var kg;
          var hin;
          var lbwkg;
          var ibwkg;

          if (isNaN(document.calc.weight.value)) {
		    alert(error_message_number);
			document.calc.weight.focus();
			document.calc.weight.value = "";
			return;
		  }
		  else {
			if (document.calc.weightUnit.value == "kg")
              kg = document.calc.weight.value;
            else
              kg = document.calc.weight.value * 0.454;
		  }

          if (isNaN(document.calc.height.value)) {
		    alert(error_message_number);
			document.calc.height.value = "";
			document.calc.height.focus();
			return;
		  }
		  else {
            if (document.calc.heightUnit.value == "m")
              m = document.calc.height.value;
            else if (document.calc.heightUnit.value == "cm")
              m = document.calc.height.value / 100;
            else
              m = document.calc.height.value * 0.0254;
		  }

          hin = m / 0.0254;

          /// LBW AND IBW
          if (document.calc.sex[0].checked) {
            lbwkg = (1.10 * kg) - 128 * ((kg * kg) / ((100 * m) * (100 * m)));
            ibwkg = 50 + 2.3 * (hin - 60);

            document.calc.lbwkg.value = Math.round(lbwkg);
            document.calc.lbwlbs.value = Math.round(lbwkg / 0.454);

            document.calc.ibwkg.value = Math.round(ibwkg);
            document.calc.ibwlbs.value = Math.round(ibwkg / 0.454);
          } else {
            lbwkg = (1.07 * kg) - 148 * ((kg * kg) / ((100 * m) * (100 * m)));
            ibwkg = 45.5 + 2.3 * (hin - 60);

            document.calc.lbwkg.value = Math.round(lbwkg);
            document.calc.lbwlbs.value = Math.round(lbwkg / 0.454);

            document.calc.ibwkg.value = Math.round(ibwkg);
            document.calc.ibwlbs.value = Math.round(ibwkg / 0.454);
          }

          // BMI
          var bmi;
          bmi = kg / (m * m);
          document.calc.bmi.value = Math.round(bmi*10)/10;

          if (bmi < 20)
            setActive("bmi1", "#FFFACF");
          else if ((bmi >= 20) && (bmi < 25))
            setActive("bmi2", "#DEFFD8");
          else if ((bmi >= 25) && (bmi < 30))
            setActive("bmi3", "#FFE9CB");
          else
            setActive("bmi4", "#FFCCCC");
        }

        function setActive(element, bgCol) {
          document.getElementById("bmi1").style.backgroundColor = "#F2FDF6";

          document.getElementById("bmi2").style.backgroundColor = "#F2FDF6";

          document.getElementById("bmi3").style.backgroundColor = "#F2FDF6";

          document.getElementById("bmi4").style.backgroundColor = "#F2FDF6";

          document.getElementById(element).style.backgroundColor = bgCol;
        }