diff --git a/cara/apps/calculator/static/js/form.js b/cara/apps/calculator/static/js/form.js
index a4ea36d5..7195b2a2 100644
--- a/cara/apps/calculator/static/js/form.js
+++ b/cara/apps/calculator/static/js/form.js
@@ -234,9 +234,17 @@ function validate_form(form) {
   return submit;
 }
 
-//function validateValue(obj) {
-//  $(obj).next('span').remove();
-//}
+function validateNonZero(obj) {
+  $(obj).removeClass("red_border");
+  $(obj).next('span').remove();
+
+  if ($(obj).val() == 0) {
+    $(obj).addClass("red_border");
+    insertSpanAfter(obj, "Value must be > 0");
+    return false;
+  }
+  return true;
+}
 
 function validateDate(obj) {
   $(obj).removeClass("red_border");
@@ -314,6 +322,10 @@ $(document).ready(function () {
   $("#total_people").change(setMaxInfectedPeople);
   $("#activity_type").change(setMaxInfectedPeople);
 
+  //Validate values > 0
+  $("input[required].non_zero").each(function() {validateNonZero(this)});
+  $(".non_zero").change(function() {validateNonZero(this)});
+
   //Validate all dates
   $("input[required].datepicker").each(function() {validateDate(this)});
   $(".datepicker").change(function() {validateDate(this)});
diff --git a/cara/apps/calculator/templates/calculator.form.html.j2 b/cara/apps/calculator/templates/calculator.form.html.j2
index 941903f1..bacb5ed3 100644
--- a/cara/apps/calculator/templates/calculator.form.html.j2
+++ b/cara/apps/calculator/templates/calculator.form.html.j2
@@ -42,10 +42,10 @@
         <span class="tooltip_text">?</span>
     </div><br>
     <input type="radio" id="room_type_volume" name="volume_type" value="room_volume" onclick="require_fields(this)" required>
-    Room volume: &nbsp;&nbsp; <input type="number" step="any" id="room_volume" class="not_zero" name="room_volume" placeholder="Room volume (m³)" min="0"><br>
+    Room volume: &nbsp;&nbsp; <input type="number" step="any" id="room_volume" class="non_zero" name="room_volume" placeholder="Room volume (m³)" min="0"><br>
     <input type="radio" id="room_type_dimensions" name="volume_type" value="room_dimensions" onclick="require_fields(this)" required>
-    Floor area: &nbsp;&nbsp; <input type="number" step="any" id="floor_area" class="not_zero" name="floor_area" placeholder="Room floor area (m²)" min="0"><br>
-    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Ceiling height: &nbsp;&nbsp; <input type="number" step="any" id="ceiling_height" class="not_zero" name="ceiling_height" placeholder="Room ceiling height (m²)" min="0"><br>
+    Floor area: &nbsp;&nbsp; <input type="number" step="any" id="floor_area" class="non_zero" name="floor_area" placeholder="Room floor area (m²)" min="0"><br>
+    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Ceiling height: &nbsp;&nbsp; <input type="number" step="any" id="ceiling_height" class="non_zero" name="ceiling_height" placeholder="Room ceiling height (m²)" min="0"><br>
     <hr width="80%">
 
     <!-- Ventilation Options -->
@@ -60,15 +60,15 @@
 
     <div id="DIVmechanical_ventilation" style="display:none">
         <input type="radio" id="air_type_supply" name="mechanical_ventilation_type" value="air_supply" onclick="require_fields(this)">
-        Air supply flow rate &nbsp;&nbsp; <input type="number" step="any" id="air_supply" class="not_zero" name="air_supply" min="0" placeholder="(m³ / hour)"><br>
+        Air supply flow rate &nbsp;&nbsp; <input type="number" step="any" id="air_supply" class="non_zero" name="air_supply" min="0" placeholder="(m³ / hour)"><br>
         <input type="radio" id="air_type_changes" name="mechanical_ventilation_type" value="air_changes" onclick="require_fields(this)">
-        Air changes per hour &nbsp;&nbsp; <input type="number" step="any" id="air_changes" class="not_zero" name="air_changes" min="0"><br>
+        Air changes per hour &nbsp;&nbsp; <input type="number" step="any" id="air_changes" class="non_zero" name="air_changes" min="0"><br>
     </div>
 
     <div id="DIVnatural_ventilation" style="display:none">
-        Number of windows: <input type="number" id="windows_number" name="windows_number" min="1"><br>
-        Height of window: <input type="number" step="any" id="window_height" class="not_zero" name="window_height" placeholder="meters" min="0"><br>
-        Opening distance: <input type="number" step="any" id="opening_distance" class="not_zero" name="opening_distance" placeholder="meters" min="0"><br>
+        Number of windows: <input type="number" id="windows_number" class="non_zero" name="windows_number" min="1"><br>
+        Height of window: <input type="number" step="any" id="window_height" class="non_zero" name="window_height" placeholder="meters" min="0"><br>
+        Opening distance: <input type="number" step="any" id="opening_distance" class="non_zero" name="opening_distance" placeholder="meters" min="0"><br>
         Windows open: <input type="radio" id="always" name="windows_open" value="always">
                       <label for="always">Always</label>
                       <input type="radio" id="interval" name="windows_open" value="interval">
@@ -81,7 +81,7 @@
     <label for="hepa_no">No</label>
     <input type="radio" id="hepa_yes" name="hepa_option" value=1 onclick="require_fields(this)">
     <label for="hepa_yes">Yes</label>
-    <input type="number" step="any" id="hepa_amount" class="not_zero" name="hepa_amount" placeholder="(m³ / hour)" min="0">
+    <input type="number" step="any" id="hepa_amount" class="non_zero" name="hepa_amount" placeholder="(m³ / hour)" min="0">
     <hr width="80%">
 
     <b>Face masks:</b>