function cnvrtb() {
  document.getElementById("theIBox").value=document.getElementById("theBox").value/2.54;
}

function cnvrta() {
  document.getElementById("theCBox").value=document.getElementById("theBox").value*2.54;
  }
  
function cnvrtm() {
  document.getElementById("theMBox").value=document.getElementById("theBox1").value/0.3048;
}

function cnvrtf() {
  document.getElementById("theFBox").value=document.getElementById("theBox1").value*0.3048;
}