function imperialVal(){
  var f = document.american;
  w = f.weight_lbs.value;
  v = f.height_ft.value;
  u = f.height_in.value;
  if (!chkw(u)){
    var ii = 0;
    f.height_in.value = 0;
  } else {
    var ii = parseInt(f.height_in.value);
  }
  var fi = parseInt(f.height_ft.value * 12);
  var i = fi + ii;
  if (!chkw(v)){
    alert("Please enter your height.");
    f.height_ft.focus();
    return;
  }
  if (!chkw(w)){
    alert("Please enter your weight.");
    f.weight_lbs.focus();
    return;
  }
  f.imperialResult.value = cal_imperialBMI(w, i);
  f.imperialResult.focus();
}

function cal_imperialBMI(lbs, ins){
  h2 = ins * ins;
  bmi = lbs/h2 * 703
  f_bmi = Math.floor(bmi);
  diff  = bmi - f_bmi;
  diff = diff * 10;
  diff = Math.round(diff);
  if (diff == 10){
    f_bmi += 1;
    diff = 0;
  }
  bmi = f_bmi + "." + diff;
  return bmi;
}

function metricVal(formVal){
  var f = formVal;
  w = f.weight_kg.value;
  i = parseInt(f.height_cm.value);
  if (!chkw(i)){
    alert("Please enter your height.");
    f.height_cm.focus();
    return;
  }
  if (!chkw(w)){
    alert("Please enter your weight.");
    f.weight_kg.focus();
    return;
  }
  f.metricResult.value = cal_metricBMI(w, i);
  f.metricResult.focus();
}

function cal_metricBMI(kg, htc){
  m = htc/100;
  h2 = m * m;
  bmi = kg/h2;
  f_bmi = Math.floor(bmi);
  diff  = bmi - f_bmi;
  diff = diff * 10;
  diff = Math.round(diff);
  if (diff == 10){
    f_bmi += 1;
    diff = 0;
  }
  bmi = f_bmi + "." + diff;
  return bmi;
}

function chkw(w){
  if (isNaN(parseInt(w))){
    return false;
  } else if (w < 0){
    return false;
  }
  else{
    return true;
  }
}