added some error handling

aromacalc.js

@@ -3,7 +3,7 @@ buttoncalc.addEventListener("click", calculate)
 
 function calculate(){
   let aromaamount = document.getElementById("aromaamount").value
-  let aromaconc = document.getElementById("aromaconc").value
+  let aromaconc = document.getElementById("aromaconc").value / 100
   let vg = document.getElementById("vg").value
   let pg = document.getElementById("pg").value
   let other = document.getElementById("other").value
@@ -13,6 +13,10 @@ function calculate(){
   let nicshotvg = document.getElementById("nicshotvg").value
   let nicshotpg = document.getElementById("nicshotpg").value
 
+  if(vg * 1 + pg * 1 + other * 1 != 100){
+  } else if(nicshotvg * 1 + nicshotpg * 1 != 100){
+  } else {
+
     document.getElementById("results").style.display="block"
     let volume = aromaamount / aromaconc
     let countnicshot = (volume * nicdose) / (nicshotamount * nicshotnicppm)
@@ -26,4 +30,4 @@ function calculate(){
     document.getElementById("amountvg").value = amountvg
     document.getElementById("amountpg").value = amountpg
   }
-
+}

index.html

@@ -12,7 +12,7 @@
               <td><input type="text" id="aromaamount" name="aromaamount"></td>
             </tr>
             <tr>
-              <td><label for="aromaconc"> Aromakonzentration:</label></td>
+              <td><label for="aromaconc"> Aromakonzentration in %:</label></td>
               <td><input type="text" id="aromaconc" name="aromaconc"></td>
             </tr>
             <tr>