function calculate() {
  document.getElementById("cubicYards").value = (document.getElementById("length").value/3) *
                                        (document.getElementById("width").value/3) *
                                        (document.getElementById("depth").value/36);
  document.getElementById("bags").value = Math.round(document.getElementById("cubicYards").value*13.5);
  document.getElementById("3cubicbags").value = Math.round(document.getElementById("cubicYards").value*9);
  return false;
}